stutter and hesitation if fuel level above 1/4 tank!

[lewisweller]

2 hours ago, wizard said:

I may be way off the mark here, but have you considered a failing/blocked catalytic converter as the possible source of stuttering/misfiring?

 

Yes, after 40 years of car ownership in Bahrain, I know what you mean :-)

 

 

I have thought about it and eliminated it for two reasons:

1. A blocked cat will usually cause issues at high rpm for obvious reasons of flow restriction. At high rpm it flies with good performance. 

2. The post cat o2 sensor is reading very stable on both banks and the dme reports the cats both pass test and readiness. 

 

Pls correct me if this is faulty diagnosis.  

[lewisweller]

Lost patients with Porsche trying to make money from warranty claim so for now decided to put newer coils back in as older one are much worse misfire. 

I decided to try and test some ohm measurements and attached is the pin 1&3 measurement for each old vs new coil for each cylinder. Note the bank 1 is where I had head gaskets blown between 2&3 cylinder show some difference in the resistance which it seem 111kohms is correct higher may spell an issue but I really can't be sure and have no reference to follow for info. The other pin combinations are high Mega ohms or open circuit.  

Also note the newer coil 2 is melted on the forth pin. I cleaned this melted stuff out and checked the plug connector which looks fine. 

I think I should replace coils 1, 2 and 3 and see of the issues are resolved. 

 

Driving feels the same less harsh misfire than the old cracked coils but stutter hesitation the same. 

 

What does anyone think about this? Any technical literature to share please on coil testing? Will be appreciated. 

 

[wizard]

The following, from elsewhere, may be relevant:-

 

Quote

 

Okay, my car is fixed!

As you predicted, ashy, there was a short circuit that was causing the coil packto overheat. The mechanic deduced this not only from the melting coil pack, but also because there was a fuse that kept blowing.

He put a bulb in place of the fuse and fiddled around with the wiring until he found the likely location of the short circuit based on how much the bulb lit up. I wouldn't have thought of that myself in a month of Sundays! It was really interesting for me to watch him work and very reassuring that I was getting a good job and not getting ripped off.

Once he figured out that the short was caused by some of the injector wires chaffing on a pipe (I guess maybe part of the cooling system) he cut out the damaged sections of the wires (there were three that had been worn through to the threads) and soldered in new sections. He tied all the wires back up and then made sure that they wouldn't chafe on the pipe again. He reckoned somebody put it back incorrectly when replacing the head gasket.

As soon as that was fixed and he fitted the new coil pack, my engine ran like a beauty! I think the problem must have been gradually getting worse because I always used to have to give it some throttle when turning the ignition but now it starts with a simple turn of the key. There is minial vibration and not the slightest hint of a misfire.

[lewisweller]

Picking up tomorrow the remaining 7 new beru zse012 coils which are same as 94860210421.

 

Also I have between 1/2 and 1/4 tank  now so will be diving back into the tank to see what can be found causing the fuel tank to read not quite full when its actually fuel to the brim. And maybe explain the sudden stall and no start event last week which hasn't returned and no codes ever appeared. 

[Brainz006]

Lewis, I've continued to follow your journey with interest -- you have my sympathies in this frustrating, long-running matter.

At the risk of jinxing myself, I wanted to provide an update regarding some of my own recent experiences that may provide some additional areas for exploration. Somewhat like you, I had a stuttering in power that was particularly noticeable (to me) in the middle RPMs under medium to full throttle, but also faintly there even under light throttle on my 06 CTT.

One day last year, I started having hot start issues after refueling, which is generally indicative of purge valve issues. So after a few months of this annoyance [having to floor the accelerator to get the engine started after refueling], I decided to check out the purge valve to see what it was actually doing.

I found that the purge valve is normally closed, thus keeping the tank vapors from being ingested. In my case, I could apply power to the purge valve with jumper leads, and it would click, suggesting that it was working. Except that as I continued to cycle the valve, it would eventually [heat up and] get stuck open (as confirmed by sucking through it - - yuck).

A stuck open purge valve would appear to act either as a vacuum leak and/or extra source of fuel - - but you'd never find it on a smoke test, because there is a check valve in front of the purge valve that keeps intake boost from pressurizing the fuel tank vent system, so you won't see it as a leak by normal means. But when it's open, the purge valve admits unmetered air/fuel to the engine.

I think the ECM, in conjunction with good O2s, is probably capable of dealing with this extra air/fuel, at least under steady conditions like idle or cruise or whenever the purge valve would ordinarily be commanded to be open. But one could envision how slow O2s and/or a bad purge valve leak would cause the ECU to hunt for the right A/F mix, particularly under dynamic situations, resulting in rough running or stuttering.

So in my case, I did an experiment - - mostly because I was sick of the hard start after fueling up. I put a vinyl/rubber vacuum cap over the intake side of the purge valve nipple, the part that the rubber​ hose slides over. I used a pick to poke a small hole in this cap (~1mm or less) and reassembled the intake hose over the cap onto the purge valve nipple.

Result:
1) No more hard starts after refueling
2) No check engine lights (I was worried about not enough vacuum being pulled on the tank and triggering an emissions issue)
3) STUTTERING UNDER ACCELERATION WAS GONE! It runs great and strong! Transmission shifts better/smoother too. Its all linked on these cars.
4) I occasionally get a faint gasoline smell in the cabin, but I think it was actually worse before my hack/test. I suspect I need new fuel filter/pump/tank gaskets. I think this is unrelated, but I wanted to mention it, because I may not be pulling as much vacuum on the tank as the factory designed given that I've restricted the purge valve.

I've driven like this now for about 3-4 months and it seems great. I bought a new replacement purge valve, but haven't gotten around to installing it.

I don't know if this hack will fix your car - - it may not given that you've reportedly already replaced your purge valve, although I suppose its possible that the replacement has also failed - - but I do think it's a simple test/fix for anyone with possible purge valve issues.

A few additional thoughts:
1) The simplest way to test this purge valve theory would be to disconnect the rubber hose from the purge valve and completely plug/cap the rubber intake hose (not the PV) with something. While this may throw a code over time, it would be a quick test of whether the purge valve is the source of your surging.
2) For those looking at this as a permanent fix, I used a small vinyl vacuum cap with small hole in it to restrict the flow. I figured that it would be held in place by the hose/clamp that went around it. It worked, but note that the cap got stuck in the rubber intake hose when I pulled the hose off after a test fit. No biggie, but I needed to thread a screw through the hole in the cap so I could fish it back out of the hose to reinstall it on the purge valve upon reassembly. Hope that makes sense.
3) There are likely other ways of restricting the rubber hose to the purge valve - - whatever you pick, make sure it won't damage your engine if it gets sucked in accidentally. Soft materials like rubber or vinyl are probably best.
4) I didn't experiment with the size of the orifice, but I'd think there's probably a sweet spot. The hole I made with the pick was pretty small, but definitely flowed air/vacuum. Start small. If you get a check engine light, consider enlarging the hole a bit more.

Lastly, and unrelated to the above fix, have you replaced the primary O2s? It made a world of difference on my 997, even though the sensors had less than 50k miles on them. Much improved running under all conditions. My guess is that the O2s get slower to respond over time, making any real-time A/F issues much more noticeable.

Hope that helps, and best wishes.



Sent from my Nexus 6 using Tapatalk

[ekstroemtj]

@Brainz006

 

Now it makes sense. I had a hesitation and strange running and vibration for month.  Changed so many parts except the purge valve (which even showed a code). Couldnt solve it. Desperate. Lewis always told me change the purge valve and finally i did. so i guess it maybe was not one of the hundreds of vacuum tubes which caused the leak. It was the purge valve :-(

[lewisweller]

2 hours ago, Brainz006 said:

Lewis, I've continued to follow your journey with interest -- you have my sympathies in this frustrating, long-running matter.

At the risk of jinxing myself, I wanted to provide an update regarding some of my own recent experiences that may provide some additional areas for exploration. Somewhat like you, I had a stuttering in power that was particularly noticeable (to me) in the middle RPMs under medium to full throttle, but also faintly there even under light throttle on my 06 CTT.

One day last year, I started having hot start issues after refueling, which is generally indicative of purge valve issues. So after a few months of this annoyance [having to floor the accelerator to get the engine started after refueling], I decided to check out the purge valve to see what it was actually doing.

I found that the purge valve is normally closed, thus keeping the tank vapors from being ingested. In my case, I could apply power to the purge valve with jumper leads, and it would click, suggesting that it was working. Except that as I continued to cycle the valve, it would eventually [heat up and] get stuck open (as confirmed by sucking through it - - yuck).

A stuck open purge valve would appear to act either as a vacuum leak and/or extra source of fuel - - but you'd never find it on a smoke test, because there is a check valve in front of the purge valve that keeps intake boost from pressurizing the fuel tank vent system, so you won't see it as a leak by normal means. But when it's open, the purge valve admits unmetered air/fuel to the engine.

I think the ECM, in conjunction with good O2s, is probably capable of dealing with this extra air/fuel, at least under steady conditions like idle or cruise or whenever the purge valve would ordinarily be commanded to be open. But one could envision how slow O2s and/or a bad purge valve leak would cause the ECU to hunt for the right A/F mix, particularly under dynamic situations, resulting in rough running or stuttering.

So in my case, I did an experiment - - mostly because I was sick of the hard start after fueling up. I put a vinyl/rubber vacuum cap over the intake side of the purge valve nipple, the part that the rubber hose slides over. I used a pick to poke a small hole in this cap (~1mm or less) and reassembled the intake hose over the cap onto the purge valve nipple.

Result:
1) No more hard starts after refueling
2) No check engine lights (I was worried about not enough vacuum being pulled on the tank and triggering an emissions issue)
3) STUTTERING UNDER ACCELERATION WAS GONE! It runs great and strong! Transmission shifts better/smoother too. Its all linked on these cars.
4) I occasionally get a faint gasoline smell in the cabin, but I think it was actually worse before my hack/test. I suspect I need new fuel filter/pump/tank gaskets. I think this is unrelated, but I wanted to mention it, because I may not be pulling as much vacuum on the tank as the factory designed given that I've restricted the purge valve.

I've driven like this now for about 3-4 months and it seems great. I bought a new replacement purge valve, but haven't gotten around to installing it.

I don't know if this hack will fix your car - - it may not given that you've reportedly already replaced your purge valve, although I suppose its possible that the replacement has also failed - - but I do think it's a simple test/fix for anyone with possible purge valve issues.

A few additional thoughts:
1) The simplest way to test this purge valve theory would be to disconnect the rubber hose from the purge valve and completely plug/cap the rubber intake hose (not the PV) with something. While this may throw a code over time, it would be a quick test of whether the purge valve is the source of your surging.
2) For those looking at this as a permanent fix, I used a small vinyl vacuum cap with small hole in it to restrict the flow. I figured that it would be held in place by the hose/clamp that went around it. It worked, but note that the cap got stuck in the rubber intake hose when I pulled the hose off after a test fit. No biggie, but I needed to thread a screw through the hole in the cap so I could fish it back out of the hose to reinstall it on the purge valve upon reassembly. Hope that makes sense.
3) There are likely other ways of restricting the rubber hose to the purge valve - - whatever you pick, make sure it won't damage your engine if it gets sucked in accidentally. Soft materials like rubber or vinyl are probably best.
4) I didn't experiment with the size of the orifice, but I'd think there's probably a sweet spot. The hole I made with the pick was pretty small, but definitely flowed air/vacuum. Start small. If you get a check engine light, consider enlarging the hole a bit more.

Lastly, and unrelated to the above fix, have you replaced the primary O2s? It made a world of difference on my 997, even though the sensors had less than 50k miles on them. Much improved running under all conditions. My guess is that the O2s get slower to respond over time, making any real-time A/F issues much more noticeable.

Hope that helps, and best wishes.



Sent from my Nexus 6 using Tapatalk
 

Brainz006 

Thanks for the reply and sharing your experiences and tips. 

I do wonder sometimes if anybody reads these long post with what some might consider mumbo jumbo or just some guy stabbing in the dark for a solution. Lol. 

 

Well I was just finishing up installing the new coils and test driving when I got your reply. 

Try to keep this short ( yeah right) here goes:

 

1. Did the new coils Fix the stutter? No! 

2. Did the coils make the power and rpm smoothness after the stutter has cleared at higher rpm better? Yes! (Not a complete waste of money then gladly and they tested very different with the multimeter old vs new coil)

3. Did disconnecting and plugging the purge valve pipe to engine as per suggestion work for me? No! (The purge valve was new last year and I think it works fine and no codes except when I unplugged it, but worth a try thanks). 

4. Whilst doing the purge valve test I found the driver side intercooler outlet to plastic pipe before the Y pipe was loose and had some oily dirt covering it. Did tightening this Fix the stutter? No! (Feels even better at high rpm, the boost doesn't feel like its tapering off so much or just my imagination).

 

The engine seems to love being thrashed, if I drive it like a animal it's lovely and flies really well. If I'm on over run down a slope to a set of traffics lights and coast to a stop it will idle Dip for sure and then after a short time at idle waiting for the light to change I pull away and its the worse stutter and hesitation as I build speed light boost comes in at light to medium or progressive throttle inputs. If I redline it then I doesn't have a chance to stutter as the rpm stays high. 

 

Brainz006 you mentioned o2 sensor precat (wide band lambda type o2 sensor in fact for us) which does make very good sense. The sensor is used for partial load and throttle demands, it goes closed loop at idle after you let off from heavy acceleration and over run to standstill. When cold the engine dotent stutter or idle Dip. 

I've already changed the passenger bank 1 pre cat sensor which was "lazy" and the other day I graphed the driver side bank 2 sensor doing the same thing! 

This b * tch is so close to being right its even more the frustrating for me. 

Bosch dealer here is strangely cheap so I may enquire about if they can get the sensor ordered in for me now as they could get anything before until March which now isn't far away. 

If this sensor isn't the final piece to this puzzle then I will stop looking and just drive it as it is. Well my wife will and she won't notice anything is wrong ......... Lol I'm having my Audi back. 

[Brainz006]

Well bummer -- I had my fingers crossed that you had a defective (new) purge valve.  In any case, I'm happy to have contributed to the cause with a quick and simple troubleshoot (and potentially long-term fix) for the purge valve.  I've appreciated your efforts to document your trouble shooting -- there's a lot of very useful information in this thread that covers the vast majority of the usual Cayenne suspects, as well as a few rare ones (such as the variocam and how to troubleshoot). 

 

A few more thoughts:

1) Definitely do the other wideband O2 -- I didn't realize your issues were part throttle only.  At startup and full throttle, the engine runs open loop, so a bad O2 wont impact (or mess up) fueling for those operating conditions.  That's my new primary suspect for your issues.

 

2) Have you tried running with one or both of your MAFs disconnected?  I believe it will throw a code, but the ECM should be able to handle it with the MAP sensor -- I've not done this myself recently, but would be happy to test it if needed for comparison.  It would be interesting to see if/how that changed your driveability issues.  Any improvement would make me suspect one or both MAFs.  I got a much better idle and low speed responsiveness when I changed the MAF on my 997 -- it had become oil fouled from the PO's use of an oiled air filter element.  MAFs and O2s are the heart of the closed loop system, so once coils and air leaks have been ruled out, those are the next most suspect parts. 

 

3) It's possible that the rubber hoses under the Y-pipe that have the check valves that go to the purge valve can be installed in such a way that they come into contact with the serpentine pulley -- Mine did and wore a hole in the rubber hose -- I've seen at least one other report of this happening on the forums.  While I don't expect that this is your issue given the scrutiny that you've given all the hoses/plumbing, it's worth noting for posterity that the section of hose that wore in my case was between the check valve and the purge valve and hence would NOT have shown up on a smoke test.  Nor would my trick of plugging the end of the hose help much, as the hole is in the middle of the run. 

 

As always, best wishes and good luck.  Feels like you're close.  It's always the last place you look....

[Brainz006]

1 hour ago, ekstroemtj said:

@Brainz006

 

Now it makes sense. I had a hesitation and strange running and vibration for month.  Changed so many parts except the purge valve (which even showed a code). Couldnt solve it. Desperate. Lewis always told me change the purge valve and finally i did. so i guess it maybe was not one of the hundreds of vacuum tubes which caused the leak. It was the purge valve :-(

 

I remember reading your posts whilst you were sorting those issues.  I didn't recall reading that it was ultimately solved by replacing the purge valve -- but agree that it now makes sense -- and you're right, a bad purge valve can cause a weird vibration at certain speeds/loads (mine did too, but the hard starting after fuel up was way more obvious).  Unfortunately I don't think I'd figured out the importance of the purge valve at that time or I would have suggested it.  Glad to hear you got it sorted.  

 

To my thinking, the general rough-running troubleshooting should probably go like this:

 

1) Scan and fix and obvious codes (with a Durametric or quality scanner that can read Porsche codes).

2) OBD2 data log the O2 sensors, long term fuel trims, and short term fuel trims, versus load and RPM.  I use the Torque App on my phone with an add-in called "Realtime Charts" -- not super-high logging rates, but still helpful.  Cheap, but somewhat time consuming.  Can also be tricky to interpret. Can be a good baseline tool -- I keep the logs for comparisons later, including after making parts changes.  Watch for LT fuel trims that are +/- more than 10% -- that usually means something is not right.  The closer ST and LT trims are to zero the better (note that ST will move around more, whereas LT moves gradually).

3) Purge valve test / block the hose to the intake.  Costs nothing.  Takes 5 mins plus a test drive.  A usual, but often overlooked suspect.

4) Fuel pump fuse test.  Just to make sure you're main pump isn't flaky.  Costs nothing.  Takes 5 mins plus a test drive.

5) Camshaft solenoid test.  Lewis's test in this thread were quite good.  My sense is that you'd do this only if you were missing low-mid range power, but OK on top.  Costs nothing.  Takes 5 mins plus a test drive.  

6) Smoke/pressure/vacuum test the intake. Can be time consuming and expensive, but is almost certainly worth it.  Most of my running issues have been leak related.

7) Coils and Plugs:  Check for cracks, measure resistance, and/or replace coils.  Change plugs while you're in there, they are relatively cheap.  Coils themselves are not cheap or quick, but an eventuality and not too terrible to DIY.  

8) Primary O2 sensors:  You may be able to see a difference between the responsiveness of the sensors on a OBD2 data log.  If you're looking to save money, change the sensor that appears less responsive first.  If a new sensor helps (and is confirmed working better by the OBD2 log) consider replacing the other one for good measure.  The parts aren't too expensive, but I have heard that one of them is a PITA to get to. Buy only Porsche or BOSCH.

9) MAFs:  I'm pretty sure the MAFs would throw an obvious CEL code, hence they would be the last thing I'd throw money at unless I'd done all the above troubleshooting and still had running issues.  But if I had done the above trouble shooting and LT Fuel Trims that were way off (+/- 10) in any of the load ranges, then that would be my next guess.  Buy only Porsche or BOSCH.

 

Hope that helps someone (and particularly so Lewis, although I think he's already done most of these in this thread, with useful explanations how to do such).  

[lewisweller]

4 hours ago, Brainz006 said:

 

I remember reading your posts whilst you were sorting those issues.  I didn't recall reading that it was ultimately solved by replacing the purge valve -- but agree that it now makes sense -- and you're right, a bad purge valve can cause a weird vibration at certain speeds/loads (mine did too, but the hard starting after fuel up was way more obvious).  Unfortunately I don't think I'd figured out the importance of the purge valve at that time or I would have suggested it.  Glad to hear you got it sorted.  

 

To my thinking, the general rough-running troubleshooting should probably go like this:

 

1) Scan and fix and obvious codes (with a Durametric or quality scanner that can read Porsche codes).

2) OBD2 data log the O2 sensors, long term fuel trims, and short term fuel trims, versus load and RPM.  I use the Torque App on my phone with an add-in called "Realtime Charts" -- not super-high logging rates, but still helpful.  Cheap, but somewhat time consuming.  Can also be tricky to interpret. Can be a good baseline tool -- I keep the logs for comparisons later, including after making parts changes.  Watch for LT fuel trims that are +/- more than 10% -- that usually means something is not right.  The closer ST and LT trims are to zero the better (note that ST will move around more, whereas LT moves gradually).

3) Purge valve test / block the hose to the intake.  Costs nothing.  Takes 5 mins plus a test drive.  A usual, but often overlooked suspect.

4) Fuel pump fuse test.  Just to make sure you're main pump isn't flaky.  Costs nothing.  Takes 5 mins plus a test drive.

5) Camshaft solenoid test.  Lewis's test in this thread were quite good.  My sense is that you'd do this only if you were missing low-mid range power, but OK on top.  Costs nothing.  Takes 5 mins plus a test drive.  

6) Smoke/pressure/vacuum test the intake. Can be time consuming and expensive, but is almost certainly worth it.  Most of my running issues have been leak related.

7) Coils and Plugs:  Check for cracks, measure resistance, and/or replace coils.  Change plugs while you're in there, they are relatively cheap.  Coils themselves are not cheap or quick, but an eventuality and not too terrible to DIY.  

8) Primary O2 sensors:  You may be able to see a difference between the responsiveness of the sensors on a OBD2 data log.  If you're looking to save money, change the sensor that appears less responsive first.  If a new sensor helps (and is confirmed working better by the OBD2 log) consider replacing the other one for good measure.  The parts aren't too expensive, but I have heard that one of them is a PITA to get to. Buy only Porsche or BOSCH.

9) MAFs:  I'm pretty sure the MAFs would throw an obvious CEL code, hence they would be the last thing I'd throw money at unless I'd done all the above troubleshooting and still had running issues.  But if I had done the above trouble shooting and LT Fuel Trims that were way off (+/- 10) in any of the load ranges, then that would be my next guess.  Buy only Porsche or BOSCH.

 

Hope that helps someone (and particularly so Lewis, although I think he's already done most of these in this thread, with useful explanations how to do such).  

Yep great summary this is. 

Pretty much details my trouble shooting journey. I have new mafs and have to admit it made absolutely no difference except long term I could rule out a failure. 

My fuel trims are always bang on LT +- 1-2%, ST +-3% accumulated less than 6%. 

 

The bank 2 sensor precat is the only thing left which is suspect given its slow reaction to snap throttle compared to the new bank 1 sensor. 

 

Blocked or partially blocked injectors or electrically failing due to heat soak is something I considered! Any thoughts? 

[Brainz006]

Your fuel trims look very good, honestly. Are they that good at all load levels, or just idle?

If that good at all load levels, it makes me question whether the problem is air/fuel related. I'd still probably do the O2 sensor, but only to have everything on an equal baseline.

Fuel injectors seem unlikely to be bad (and are more expensive to fix, although a few bottles of Techron never hurt). Dirty/clogged injectors usually make for a poor idle, especially when cold, and heat soak/electrical issues would hurt your full throttle, not just mid range. Also, I would expect the ST fuel trims to go crazy if the injectors had a temperamental electrical issue.

Is it possible you're having transmission shudder and not engine stutter - - they can feel similar? An underfilled transmission is very easy to do on these cars, especially if you accidentally pinch the trans filter oring - - ask me how I know. And an underfilled trans will do odd things - - it might slip or shudder ever so slightly while driving, particularly at lower speeds and RPMs because the trans will not smoothly apply the torque converter lockup which happens between 1500 and 2500 rpm. I remember the issue being worse when cold, not hot, so that may not be it.

How old is the ATF? What brand/type? Mobil 3309/Toyota Type IV is the factory spec, and is what I've used successfully (once the fill level issue got sorted). If you turn off PSM, or manually shift such that RPMs are above 3000rpm when you change gears, does that alleviate your stuttering?

I'm otherwise out of ideas for now. But I'm still stumbling upon odd revelations about the Cayenne after almost 5 years of ownership. For example, this weekend I learned that a low battery will reduce the maximum HVAC blower speed and make you think your fan controller is failing. It's happened a bunch of times, but I never realized it was due to low battery voltage after sitting for a week (the battery needs replacing). I write back if I think of anything else.

Good luck and best wishes.

Sent from my Nexus 6 using Tapatalk

[lewisweller]

7 minutes ago, Brainz006 said:

Your fuel trims look very good, honestly. Are they that good at all load levels, or just idle?

If that good at all load levels, it makes me question whether the problem is air/fuel related. I'd still probably do the O2 sensor, but only to have everything on an equal baseline.

Fuel injectors seem unlikely to be bad (and are more expensive to fix, although a few bottles of Techron never hurt). Dirty/clogged injectors usually make for a poor idle, especially when cold, and heat soak/electrical issues would hurt your full throttle, not just mid range. Also, I would expect the ST fuel trims to go crazy if the injectors had a temperamental electrical issue.

Is it possible you're having transmission shudder and not engine stutter - - they can feel similar? An underfilled transmission is very easy to do on these cars, especially if you accidentally pinch the trans filter oring - - ask me how I know. And an underfilled trans will do odd things - - it might slip or shudder ever so slightly while driving, particularly at lower speeds and RPMs because the trans will not smoothly apply the torque converter lockup which happens between 1500 and 2500 rpm. I remember the issue being worse when cold, not hot, so that may not be it.

How old is the ATF? What brand/type? Mobil 3309/Toyota Type IV is the factory spec, and is what I've used successfully (once the fill level issue got sorted). If you turn off PSM, or manually shift such that RPMs are above 3000rpm when you change gears, does that alleviate your stuttering?

I'm otherwise out of ideas for now. But I'm still stumbling upon odd revelations about the Cayenne after almost 5 years of ownership. For example, this weekend I learned that a low battery will reduce the maximum HVAC blower speed and make you think your fan controller is failing. It's happened a bunch of times, but I never realized it was due to low battery voltage after sitting for a week (the battery needs replacing). I write back if I think of anything else.

Good luck and best wishes.

Sent from my Nexus 6 using Tapatalk
 

With psm off it inadvertently disguises the issue as the rpm is held higher. If shifting manually psm off or on its not much different really, I would say marginally better only for the fact when you WOT it won't kick down and this generally mean the rpm and boost build slower and more steadily possibly allowing for a better mixture and combustion in that particular circumstances verses being in auto and it kicks down and flies off with a stutter upon pickup. 

 

Transmission is a good out to the box idea, the fluid is Toyota type iv and around 8 litres or so went in with new filter etc and new mounts, when head gaskets where done. Also transfer fluid replaced just recently 1 litre of type iv. I do get the "four wheel drive faulty" warning sometimes not necessarily at any logical time. This is the stepper motor and or control unit faulty so I've read. I just ignore it and next time I cycle ignition it's gone again and never found a code. 

 I have to say the transmission is very smooth especially for 11 year old car after 125k km. Smoother than the Audi s-tronic in certain circumstances. 

 

This morning I disconnected the bank 2 precat lambda sensor and no check light or perceivable difference in driving the last 20km. Strange! 

 

Will check for a code which will obviously say open circuit........  Bank 2 sensor 1. 

 

So for now only thing to do is replace this sensor and recheck. 

[Brainz006]

Do you notice the stutter more on an upward or downward slope? That could indicate low ATF, as it may aerate the fluid and cause weird issues. Mine was most noticeable on the first drive of the day and when driving slowly up hills.

Honestly though, other than a bad valve body and under filled trans, the next most common stutter issue I experienced was a vacuum leaks. One was the tee behind the manifold, and the other was the fitting that snaps on to the bottom of the Y pipe - - it wasn't fully seated and created a big leak. And then there was the time my LHS boost pipe from the turbo to IC popped off (because I'd not seated it correctly). In all cases, rough running in the low to mid range, but OK up top (except the boost pipe issue obvs). The boost pipe error throws a PRND trans error, BTW.

Good luck.

Sent from my Nexus 6 using Tapatalk

[lewisweller]

2 hours ago, Brainz006 said:

Do you notice the stutter more on an upward or downward slope? That could indicate low ATF, as it may aerate the fluid and cause weird issues. Mine was most noticeable on the first drive of the day and when driving slowly up hills.

Honestly though, other than a bad valve body and under filled trans, the next most common stutter issue I experienced was a vacuum leaks. One was the tee behind the manifold, and the other was the fitting that snaps on to the bottom of the Y pipe - - it wasn't fully seated and created a big leak. And then there was the time my LHS boost pipe from the turbo to IC popped off (because I'd not seated it correctly). In all cases, rough running in the low to mid range, but OK up top (except the boost pipe issue obvs). The boost pipe error throws a PRND trans error, BTW.

Good luck.

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Interesting stuff. The stutter is worse up hill but I think more to do with the load rather than the angle and fluid slosh. Downhill better obviously less load but not a miracle Fix or even close to being. 

 

The whole day was driving and idling and driving stop and then again driving. The car hates to be at idle for a while then drive, its a real pig at that time. Light throttle also it hates. Thrashing it all the time is the only way it feels ok. It almost like it wants to clear it's throat. 

Light throttle cruising with small increase and decreases in speed and load is also crap, roughness and shudders with a vibration feeling and sounds like it's missing if you give a brief bit of gas. Bucks if you boot it at that point as the boost comes in and it takes off. I also get a quite Jerky and bang noise during lift off like it wasn't ready for it. 

 

I may remove the inlet manifold and address the rear turbo vent pipes which are obviously leaking a bit from the crimped metal to hose floating adaptors fitting. Maybe I find something I didn't find last time I had it off. 

 

My engine whines does yours? In sequence with the rpm so it's something rotating. Other people have said the same they hear it and have looked for the source of the whine without finding. 

 

Edited February 20, 2017 by lewisweller

[Brainz006]

Mine does not really whine noticeably -- some whirring from the rotating bits, but not much. There's a bit of clicking from the fuel injectors, but it's otherwise pretty quiet -- mostly a fan/blowing noise. My CTT only has ~50k miles, so that might make a difference. Assuming you're already ruled out the AC compressor, alternator, or power steering, by doing different things to increase/decrease the load on those components, I have heard that a useful way to diagnose an engine whine is to remove the serpentine belt and run the engine for a SHORT amount of time to compare the noise with and w/o the belt.

No noise without the belt means you know where to look: idler pulleys, alternator, water pump, etc. I've had luck disassembling idler pulleys and repacking them with fresh grease on other cars, which can reduce rotating noise. If your noise is still present with the serp belt removed, then it must be something else (including maybe an intake leak) that's making the noise. Just to state the obvious for posterity, you don't want run your engine without the serpentine belt for very long as it will quickly overheat (as the water pump will not be turning) -- so only test for a minute or so, while cold, to check for whether the sound changes.

The more I think about your issues and compare them with things I've experienced and subsequently fixed on my CTT, I think you have an intake leak. Your symptoms most closely match the time the line that snaps onto the bottom of the Y pipe was not plugged in -- my car bucked and stumbled at light throttle and low rpm and felt like it had bad driveline lash -- you couldn't be smooth with the throttle at low speed. I never got any error messages or CELs. It was annoying as hell.

And I'm wondering if there is some vacuum tubing behind a check valve (like the purge valve was) that would not otherwise be easily tested by a smoke test. Or maybe the tee or crimped connectors at the back of the manifold that you've mentioned. Or perhaps the leak is in one of the corrugated or black plastic lines under the shrouds at the top of the valve covers or to the brake booster (although a leak on that line will throw a code and make the brake vacuum pump run and get hot -- BTDT). One other idea would be the AOS membrane, but I seem to remember that you checked that, and I hear they whistle or honk or cause voluminous smoke out the tailpipe (I can confirm the latter when I accidentally reassembled my AOS the wrong way after opening it up to examine it).

There's a vacuum piping schematic on a sticker on the hood slam panel above the radiator on my car. It takes a bit of time to figure it out because its more a flowchart than a scale diagram, but it's pretty useful for figuring out what the various lines are supposed to be doing. I keep meaning to make a copy of the sticker and color code the lines with a description of where the valves and connecting parts are located, as it would be very helpful for troubleshooting the vacuum system (or keeping track of what vacuum lines you've tested!). There's a lot of places for the Cayenne's vacuum lines to have an issue, especially as the plastic ages an gets brittle.

As always, hope something above helps you or someone else. Best of luck.



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[lewisweller]

On 21/02/2017 at 8:48 AM, Brainz006 said:

Mine does not really whine noticeably -- some whirring from the rotating bits, but not much. There's a bit of clicking from the fuel injectors, but it's otherwise pretty quiet -- mostly a fan/blowing noise. My CTT only has ~50k miles, so that might make a difference. Assuming you're already ruled out the AC compressor, alternator, or power steering, by doing different things to increase/decrease the load on those components, I have heard that a useful way to diagnose an engine whine is to remove the serpentine belt and run the engine for a SHORT amount of time to compare the noise with and w/o the belt.

No noise without the belt means you know where to look: idler pulleys, alternator, water pump, etc. I've had luck disassembling idler pulleys and repacking them with fresh grease on other cars, which can reduce rotating noise. If your noise is still present with the serp belt removed, then it must be something else (including maybe an intake leak) that's making the noise. Just to state the obvious for posterity, you don't want run your engine without the serpentine belt for very long as it will quickly overheat (as the water pump will not be turning) -- so only test for a minute or so, while cold, to check for whether the sound changes.

The more I think about your issues and compare them with things I've experienced and subsequently fixed on my CTT, I think you have an intake leak. Your symptoms most closely match the time the line that snaps onto the bottom of the Y pipe was not plugged in -- my car bucked and stumbled at light throttle and low rpm and felt like it had bad driveline lash -- you couldn't be smooth with the throttle at low speed. I never got any error messages or CELs. It was annoying as hell.

And I'm wondering if there is some vacuum tubing behind a check valve (like the purge valve was) that would not otherwise be easily tested by a smoke test. Or maybe the tee or crimped connectors at the back of the manifold that you've mentioned. Or perhaps the leak is in one of the corrugated or black plastic lines under the shrouds at the top of the valve covers or to the brake booster (although a leak on that line will throw a code and make the brake vacuum pump run and get hot -- BTDT). One other idea would be the AOS membrane, but I seem to remember that you checked that, and I hear they whistle or honk or cause voluminous smoke out the tailpipe (I can confirm the latter when I accidentally reassembled my AOS the wrong way after opening it up to examine it).

There's a vacuum piping schematic on a sticker on the hood slam panel above the radiator on my car. It takes a bit of time to figure it out because its more a flowchart than a scale diagram, but it's pretty useful for figuring out what the various lines are supposed to be doing. I keep meaning to make a copy of the sticker and color code the lines with a description of where the valves and connecting parts are located, as it would be very helpful for troubleshooting the vacuum system (or keeping track of what vacuum lines you've tested!). There's a lot of places for the Cayenne's vacuum lines to have an issue, especially as the plastic ages an gets brittle.

As always, hope something above helps you or someone else. Best of luck.



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A picture of that vacuum piping diagram would be good please. 

Really I have to take off the manifold again and cut off those rigid pipe adaptors and put in a hydraulic pipe instead with jubilee clamps. Maybe I will find something else wrong whilst I'm looking in there. 

 

Any one have some info about exactly how the transfer case works? If I drop into neutral the car seems so smooth in gear it's a stumbling pig. Engine and or drive train I'm not sure. 

[Brainz006]

Transfer case has a chain in it that reportedly gets stretched over time, but it doesn't make sense that would be your issue. There's also the hi/lo motor that reportedly gets frozen, but from reading, that gives an error light but no drive ability issues.

Here's the piping diagram. Let me know if this diagram doesn't come through in high resolution and I'll PM you.

Your symptoms sound most like the time my line that goes from the Y pipe to the brake jet pump didn't get fully seated under the Y pipe. That particular line also connects on the back of the manifold, but seems like if you had a crack on the manifold side of the jet pump that you'd get a brake booster error. So seems like from the jet pump to Y pipe would be most suspect.

Good luck.



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[lewisweller]

3 hours ago, Brainz006 said:

Transfer case has a chain in it that reportedly gets stretched over time, but it doesn't make sense that would be your issue. There's also the hi/lo motor that reportedly gets frozen, but from reading, that gives an error light but no drive ability issues.

Here's the piping diagram. Let me know if this diagram doesn't come through in high resolution and I'll PM you.

Your symptoms sound most like the time my line that goes from the Y pipe to the brake jet pump didn't get fully seated under the Y pipe. That particular line also connects on the back of the manifold, but seems like if you had a crack on the manifold side of the jet pump that you'd get a brake booster error. So seems like from the jet pump to Y pipe would be most suspect.

Good luck.



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Thanks for the diagram.

What is the "jet pump"?

Do you think the manifold has some internal chamber at the rear where all those pipes connect? I did wondered this before but after changing the pipes and checking the check valves everything looked good to go. Am I right in saying the manifold itself has nothing else moving or adjustable inside (like some have variable track length etc) 

The more I rack my brain and the more I drive and listen to when its doing the stumbling there is a noise constant with it, this rules out really a drive train type problem for me. It really does sound like a missing pop pop pop but really fast with the rpm. Like the ruler hanging from the table edge and you ping it down then it starts to move up and down and then slide the ruler to make it shorter and the frequency increases. 

 

Edited February 22, 2017 by lewisweller

[Brainz006]

The jet pump is a venturi pump that's part of the vacuum lines that go to the brake booster. Under closed throttle, vacuum from the back of the motor suctions across the jet pump (which may have an embedded check valve, not sure) and keeps vacuum on the brake booster. Under boost, pressurized air from under the Y pipe flows across the jet pump to impart a venturi vacuum on the brake booster. That way the brakes have vacuum at idle or full throttle.

I have no idea what all the little lines do at the back of the intake manifold nor whether there is anything moveable inside (but I don't think so). Seems possible but likely unnecessary on a turbo engine as you don't really need an adjustable intake length to make power - - the turbos have that covered (and is consistent with how Porsche does it on the 997s, i,e, the turbo models have a simpler manifold). That said, there is some sort of strangeness at the back of the manifold including the little jumper line that go from the manifold back to the manifold - - I'd love to know what that's for.

Could the big corrugated vacuum lines on the top front of the intake manifold have a crack that makes a resonant sound at different engine speeds? The ones that go to 2-way AOS check valve....?





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[lewisweller]

The jet pump is where because I only see a little cyclinder diagram 3 part number 4 (venturi tube), blow up in picture 4 which must be it? Your referring to pipe 12 in the first diagram and yes it new when head gaskets were done. I also leak checked t a few months ago when I had the manifold off and starter motor out. The small Tee 25 labelled in second diagram at the back is the connection to the turbo vent rigid metal lines which leaks. This is the leak I intend to cut all out and replace with a hose and two jubilee clips. 

When I tried to blow or suck those rigid turbo vent lines 18 and 20  I couldnt get anything in or out which was strange for a "vent line" ! That oil collection block 6 and 7 must be having a non return check valve or something inside and looks more complicated than it might first seem possibly internally?

[Brainz006]

The jet pump is where because I only see a little cyclinder diagram 3 part number 4 (venturi tube), blow up in picture 4 which must be it? Your referring to pipe 12 in the first diagram and yes it new when head gaskets were done. I also leak checked t a few months ago when I had the manifold off and starter motor out. The small Tee 25 labelled in second diagram at the back is the connection to the turbo vent rigid metal lines which leaks. This is the leak I intend to cut all out and replace with a hose and two jubilee clips. 
When I tried to blow or suck those rigid turbo vent lines 18 and 20  I couldnt get anything in or out which was strange for a "vent line" ! That oil collection block 6 and 7 must be having a non return check valve or something inside and looks more complicated than it might first seem possibly internally?

Diagram 1:
Jet pump: Yes, I believe it's molded into #4, and is back by the firewall at the back of the manifold -- not sure whether the cylinder is the jet pump or the checkvalve after the jet pump, but same area. One thought: #4 has those weird squeeze fittings on both ends. Make sure both ends of #4 are firmly seated on the respective nipples -- it's easy to not get them fully seated.

Good that Pipe 12 is new. Can cross that off the list for now. See Diagram 3, Pipe 5 below.

Diagram 2:
Yes Tee 25 is notorious for cracking/crumbling. If you've not replaced that, definitely start by replacing it with a brass or aluminum tee. There are two crimped fittings each on the turbo vent lines 18 and 20 at the back of the manifold -- are those the fittings you suspect of leaking? I remember some modest play in mine, but I don't remember thinking they might leak. I have no idea the exact function of 18 and 20, although I suppose they allow the turbo oil catch tank to breathe which keeps the oil flowing freely to the sump. Strange that you cant blow/suck through them, although I suppose maybe you're trying to blow/suck the oil in the drain line too, which could be difficult.

Another thought: With the engine running, if you place your palm (or a sheet of paper) over the uncovered oil fill hole on the valve cover, is there good vacuum?

Diagram 3:
The other corrugated pipe I was thinking of was #5: As best I can tell, it's the main crankcase vacuum line. If you don't have crankcase vacuum per the test above, that line or the AOS would be suspect. That's big vacuum line. Also check the "turbo check valves" that it attaches to -- it's the "3-leg L fitting" that connects to the AOS spigot. I just had another thought: I believe it's possible to install the turbo check valve a couple ways (but there's only one right way -- the leg you can blow into goes to the AOS spigot on the valve cover). I suppose if you rotated the check valve clockwise one position, the valve would accidentally function as a giant intake leak. It's worth confirming that's not the case.

Lastly, all the little hoses and connectors from #25 to the purge valve are suspect until proven otherwise. It's those hoses that can rub on the belt pulley under the Y pipe. I suppose a quick test of that plumbing (and the purge valve) would be to temporarily plug #25 at the manifold and see what happens -- similar to the purge valve test.

Best wishes.





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[lewisweller]

On 23/02/2017 at 8:39 AM, Brainz006 said:

 

Diagram 1:
Jet pump: Yes, I believe it's molded into #4, and is back by the firewall at the back of the manifold -- not sure whether the cylinder is the jet pump or the checkvalve after the jet pump, but same area. One thought: #4 has those weird squeeze fittings on both ends. Make sure both ends of #4 are firmly seated on the respective nipples -- it's easy to not get them fully seated.

Good that Pipe 12 is new. Can cross that off the list for now. See Diagram 3, Pipe 5 below.

Diagram 2:
Yes Tee 25 is notorious for cracking/crumbling. If you've not replaced that, definitely start by replacing it with a brass or aluminum tee. There are two crimped fittings each on the turbo vent lines 18 and 20 at the back of the manifold -- are those the fittings you suspect of leaking? I remember some modest play in mine, but I don't remember thinking they might leak. I have no idea the exact function of 18 and 20, although I suppose they allow the turbo oil catch tank to breathe which keeps the oil flowing freely to the sump. Strange that you cant blow/suck through them, although I suppose maybe you're trying to blow/suck the oil in the drain line too, which could be difficult.

Another thought: With the engine running, if you place your palm (or a sheet of paper) over the uncovered oil fill hole on the valve cover, is there good vacuum?

Diagram 3:
The other corrugated pipe I was thinking of was #5: As best I can tell, it's the main crankcase vacuum line. If you don't have crankcase vacuum per the test above, that line or the AOS would be suspect. That's big vacuum line. Also check the "turbo check valves" that it attaches to -- it's the "3-leg L fitting" that connects to the AOS spigot. I just had another thought: I believe it's possible to install the turbo check valve a couple ways (but there's only one right way -- the leg you can blow into goes to the AOS spigot on the valve cover). I suppose if you rotated the check valve clockwise one position, the valve would accidentally function as a giant intake leak. It's worth confirming that's not the case.

Lastly, all the little hoses and connectors from #25 to the purge valve are suspect until proven otherwise. It's those hoses that can rub on the belt pulley under the Y pipe. I suppose a quick test of that plumbing (and the purge valve) would be to temporarily plug #25 at the manifold and see what happens -- similar to the purge valve test.

Best wishes.





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Brainz006 

Most of the above is either checked or replaced. 

 

 

Today I did some interesting graphs of the bank 1 and 2 precat lambda sensors. Scannerdanner is the bomb at diagnosing using data. Helps to have a scope. Big Props to him. 

 

Note: snap throttle test of bank 2 sensor compared against bank 1 sensor shows its not showing a peak rich condition and also produces a steady but lower than normal amperage. Unless fuel is the issue on just one bank then this points at the lambda sensor I believe. If extra air (vacuum leak, pretty hard on a shared manifold to only affect one bank) was the issue then fuel would be added and the lambda sensor would show that. 

 

Driving the car shows something is wrong with bank 2 (old sensor) whereas bank 1 (new sensor) looks to be working great as you would expect. 

The first and second screen shot shows me driving at full throttle, bank 2 sensor doesn't go peak rich, it's goes up some but not enough, bank 1 is pinned peak rich high until the gear change which is the Dip then peaks again. So initial conclusion would say this old sensor is just knackered but does enough to not set off a code. 

The 3rd and 4th screen shot is the short term fuel trims of bank 1 Green and bank 2 blue immediately after I reset the DTC codes which clears the fuel trims and start the dme learning process. Look how the green line bank 1 starts at rich and then lean adjusting to find the fuel trim setting required. Bank 2 blue line is flat lining doing nothing. So unless I have a fuel/air issue which I'm thinking how this could be on one bank and make the sensor behave like this it can only be the sensor? 

This also explain why when driving with the bank 2 sensor disconnected it's makes no difference to the running. 

Due to this sensor I'm running lean on bank 2 at mid to full throttle and hence the hesitation!!

 

Sensor ordered already from AutoHaus 80dollars. 

 

Tomorrow will do propane test to make sure it's not a lack of fuel! Both sensors if working properly will spike a peak rich regardless of any fuel  injection or vacuum leak if I'm pumping propane in via the MAP sensor hole briefly lift it up to add. 

 

If this doesn't Fix It I may torch it.  

 

 

Edited February 24, 2017 by lewisweller

[Brainz006]

That 02 sure does look suspicious and makes perfect sense for your symptoms (only hot and mid throttle, precisely when the O2s are supposed to be doing their job). Fingers crossed you found the issue.

And Yes. The Scanner Danner YouTube vids are highly educational. Completely recommended for learning how to troubleshoot with a scanner. I successfully used that on diagnosing my 997's issues (which as I noted earlier in the thread, I did see a meaningful improvement with new O2s despite low mileage - - I think they got fouled).

I'm really hoping this is it. Good luck

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[lewisweller]

16 minutes ago, Brainz006 said:

That 02 sure does look suspicious and makes perfect sense for your symptoms (only hot and mid throttle, precisely when the O2s are supposed to be doing their job). Fingers crossed you found the issue.

And Yes. The Scanner Danner YouTube vids are highly educational. Completely recommended for learning how to troubleshoot with a scanner. I successfully used that on diagnosing my 997's issues (which as I noted earlier in the thread, I did see a meaningful improvement with new O2s despite low mileage - - I think they got fouled).

I'm really hoping this is it. Good luck

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What still has my head scratching is why when the sensor doesn't show a peak rich condition the dme identify that as a problem and do something? Seems a basic red flag for performance Mr Bosch, err hello I'm full throttle but sensor says I'm not rich wtf something is wrong Mr dme. And if not showing rich the dme should add fuel short term and long term to compensate!

This is why I'm going to do the propane test because if I didn't learn anything from the last year working on this b * tch car it is that despite finding some real issues they are not proving to be the actual cause of the mother f**k*** "STUTTER" . 

[ekstroemtj]

@ Lewis

 

by the way did you check all the electric wiring in the engine bay?  Age and of course temperature changing makes them briggle. When i saw my headlight wiring i can imagine others looks soon the same. Today i found the reason for my CEL. The wiring to the purge valve was damaged.