2006 Cayenne Turbo Misfire

[DannyHoffman]

 

My very recently acquired 2006 Turbo S 73,000 miles started misfire yesterday shortly after filling the tank with petrol.
The more I drove the worse it got until the point where it cut out completely and the engine check light came on.
I restarted and limped home

I have a Maxidiag EU 702 fault reader which supports a number of car manufacturers but not Porsche.
However the generic OBDII mode and the VW specific mode read the following errors:

P0492 Secondary Air Injection System Insufficient Flow Bank 2
P2177 System Too Lean Off Idle Bank 1
P2179 System Too Lean Off Idle Bank 2
P0300 Random Multiple Cylinder Misfire Detected
P0301 Cylinder 1 Misfire Detected
P0302 Cylinder 2 Misfire Detected
P0306 Cylinder 6 Misfire Detected
P0305 Cylinder 5 Misfire Detected

It felt like coil packs and was due a new set of plugs so I changed them all today.

Whilst doing so I noticed that the hose to the secondary air pump on bank 2 was completely disconnected, possibly explaining the first 3 errors

I couldn't see any cracks on the coil packs and their part number ended in 07 which from what I have researched means they were manufactured in 2009 ish, around the time of the last plug change

The plugs were all a similar very dark colour.

I cleared the errors and the check engine light now stays off.

Is there anything that could cause a misfire on all 4 of the front cylinders only?

I have visually inspected all the vacuum hoses.

Drove it again and it definitely still isn't 100% right. I got an occasional minor stutter both cold and hot.

Fault reader now only had the following:

P2177 System Too Lean Off Idle Bank 1
P2179 System Too Lean Off Idle Bank 2

I cleared them and it still misfired, but I only drove a short way and the codes didn't return.

I looked back through the limited service history I have for the car and in April this year the car was taken for a diagnostic test. The hand written report has the following:

1) Secondary Air System Bank 2 Below Limit Value
2) Vehicle Electrical System Voltage Via Main Relay. No Signal

It doesn't give the P numbers.

I'm assuming the first error was due to the secondary air pump hose being disconnected, could this have been off since the last plug change in 2010?

The second error is a little less clear from a quick look on the forums. One post suggests it is to do with parking assist, another to do with a faulty relay for the fuel pumps and another for a low battery voltage.

After reading the forums I found a few suggestions that low battery voltage could cause strange misfire issues so I attached a trickle charger overnight which showed the battery charge was less than 80% charged. My car has done very few miles in the last year and since I've had it I've been doing various bits and pieces which would drain the battery (tailgate shocks, tracing a Bose amp fault) and only done short journeys.

I also read about the PCV/Oil air separation membrane and have checked mine. It has a 1/4 inch split and a smaller pin hole. I have temporarily put a dab of glue and some tape on these. A new one is on order.

The engine now has a lovely creamy feel to it 99% of the time, smoother than any of the other Cayennes I test drove whilst looking.

There were no fault codes logged but I'm am still getting a very occasional stutter.

After getting the battery 100% charged I then tested the battery and it was indeed failing, so I fitted a new one.

The new membrane arrived so I fitted that.

All was well for a week until I filled up, and then about 5 miles later it started to stutter occasionally about 3 times over a 5 mile journey.

The battery voltage is good (12.9v when the car is turned off and locked). No faults have been logged

Could having a full tank of fuel cause a problem?

Any other ideas? 

[wizard]

Whilst I really can't see that the quantity of fuel put in would affect anything, the quality would be a different matter.

 

Too much of a coincidence to me.

Edited October 8, 2017 by wizard

[DannyHoffman]

I filled up both times with Shell V Power at different petrol stations

[wizard]

Does your handbook stipulate such a high octane petrol? If not, perhaps you might try a lower octane (95) and see if that remedies the problem.

Edited October 8, 2017 by wizard

[DannyHoffman]

The sticker inside the filler flap says 95/98, the handbook says the engine is optimised to run on 98. Shell V-Power is 99, so it's an interesting suggestion

[wizard]

I have read somewhere/sometime that too high an octane can be interpreted as the mixture being too lean. 

 

You may want to verify that, and also see whether a 50:50 mix of 99 and 95 gives you a 97. I would hasten to add that I'm not a petroleum engineer by any stretch of the imagination .....

[Loren]

The current coil packs are: 948 602 104 21. You are about 3 revs behind.

 

 

[DannyHoffman]

"The current coil packs are: 948 602 104 21. You are about 3 revs behind. "

I changed them all even though the old ones didn't have any cracks 

 

[Brainz006]

Sounds like it was the low battery if most symptoms disappeared after you charged it up. What battery voltage do you have after the car has sat for 72 hours? How about right after a crank after sitting a day or two?

Likely suspects for minor, occasional stuttering can be coils or a leaking purge valve. Neither will throw a code until they get really bad (and even then they might not code).



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[lewisweller]

Octane 95/97/99 won't change anything adversely. Higher Octane will actually reduce knock, allow more ignition advance and increase power and torque with less risk of pre-ignition. So higher Octane equals less chance of stuttering.

 

Evap purge valve possibly could be leaking by? 

 

Left fuel pump weakness is quiet common!

Try switching to the right side pump (remove fuse for left pump and cycle the ignition and start) when tank is over 1/2 full, fill it up and see if it will stutter. The fact the last two cylinder on each bank was the issue before suggests fuel pressure and or flow is low hence the last two injectors on each bank are the lacking fuel. In theory anyway. 

 

Also check your fuel pressure regulator is running at 4 bar during idle and revving. Should hold 3bar after 10 mins when engine is switched off. 

[wizard]

Just one other thought and then I'll shut up about octane !

 

If the previous owner was running 95 and then 99 is put in by you, I wonder if there's a Porsche-specific fuel adaptation procedure (re-learning process) to be followed or if adaptation is automatic and immediate?

[Brainz006]

Lewis is correct. Higher octane will generally only help (until you get to race levels of octane : 105+). Octane is not your problem, although perhaps bad gas could be. Need answers to the prior questions first.

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[DannyHoffman]

I had to do an early airport run this morning and didn't want to risk any problems so stuck the trickle charger on last night as a precaution.

 

It ran faultlessly all day to day.

 

Thanks all for the suggestions.

 

Re the evap purge valve, would loosening the fuel filler cap eliminate this if it starts to stutter again? 

 

Re fuel pump/pressure - I would have thought this would be more likely to be the cause at higher revs, when it plays up it is worst between 1,600 and 2,000 revs at light throttle

[Brainz006]

It sounds like it was your battery if it’s now running flawlessly. The purge valve (like other vacuum leaks) causes stumbles off idle and odd shifting below 2500 rpm. Opening the fuel cap won’t help (and might make it worse depending on how badly the purge valve was leaking), and would ultimately throw another code given time.

Take your car to Autozone, or similar, and have them load test the battery. If it’s weak, replace it. In my neighborhood (Texas), Home Depot has the best deal on compatible batteries.


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[wizard]

You shouldn't need to be trickle charging a brand new battery unless it's duff out of the box, there's a charging problem or a parasitic drain.

 

It's relatively easy to rule those in or out with a multimeter.

[DannyHoffman]

I have tested the new battery under load and after the car has been sitting overnight and it appears to be fine - 12.9v with the engine off and everything else turned off. I am getting 14.2v at idle so the charging system seems to be healthy too.

 

Is there a way to test the purge valve for leaks or is it just a case of replacing it ?

 

[lewisweller]

4 hours ago, DannyHoffman said:

I have tested the new battery under load and after the car has been sitting overnight and it appears to be fine - 12.9v with the engine off and everything else turned off. I am getting 14.2v at idle so the charging system seems to be healthy too.

 

Is there a way to test the purge valve for leaks or is it just a case of replacing it ?

 

Disconnect ( open unclip) the pipe of 3 at the rear of bank 2 side almost directly under the SAI pump where it goes into a flexible hose 33, pipe sits in the injectors area.

Then blow down the rigid pipe which is assembled as part of the purge valve 3. It should be shut when powered off. So normal closed, power signal from dme to open I believe. 

It was the first thing I replaced on mine but I had a code! P0441 or p0444, one of them

 

[DannyHoffman]

I had a quick look at testing the purge valve as suggested, but am a bit nervous I might break it removing the hoses. And as I don't have a spare I could render the car undriveable.

 

If I were to clamp the flexible hose at the front of the engine with a brake hose clamp next time it starts to stutter would this eliminate the purge valve?

 

I have also ordered a volt meter that plugs into cigarette lighter (which has yet to arrive) so I can monitor the voltage in real time next time it stutters 

 

I expect to be filling the tank in the next day or so, so watch this space!

Edited October 12, 2017 by DannyHoffman

[Brainz006]

Plugging/clamping the intake side rubber hose that connects to the purge valve might give you a positive result and would suggest/confirm a failed purge valve (which essentially allows a vacuum leak through the gas tank).

You can also use a soft rubber vacuum cap with a tiny hole drilled in it (0.5mm) to choke the amount of vacuum allowed through the valve. The cap can easily be installed on the intake side valve nipple, and then reinstall the rubber intake hose over both the cap and nipple. While this fix will help a failed purge valve, the car will generally run more smoothly if you just replace the valve.

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[DannyHoffman]

Well yesterday I had to fill up half way through a 60 mile motorway run. 

 

True to form a few miles after the fill up it started to stutter. I pulled over and fitted the brake hose clamp to the flexible hose at the front of the purge valve, but it was still the same. I loosened the tank filler cap and it was still the same.

 

I got within half a mile of my home before it became difficult to drive.

 

The fault code reader showed:

 

P0441 EVAP Emission control Sys incorrect flow

 

which I assume is because I had blocked the purge valve pipe or removed the fuel cap. I cleared the error.

 

Battery voltage with the car off and locked was 12.79v measured under the bonnet.

 

I put the trickle charger on overnight just in case.

 

It drove perfectly this morning 

[wizard]

Bizarre!

 

So, for the first 30-odd miles of your journey yesterday it was fine? It then acts up to the point of stalling altogether after filling the tank but is fine everyday thereafter? Are you putting it on trickle charge every night?

[DannyHoffman]

I only trickle charge it after it starts playing up, or if I am making a longer journey when it would be inconvenient if it broke down. I have done short journeys without trickle charging it for over a week and had no problems.

 

Two things appear certain 

 

1) It always plays up within 5 miles of filling up, whether motorway miles or around town

 

2) Trickle charging it overnight cures it till the next fill up

 

I might try only half filling the tank next time

 

 

[wizard]

3 hours ago, DannyHoffman said:

 

I might try only half filling the tank next time

 

Quote

 

Shooting in the dark here but might I also suggest that before filling, you go through the motions of filling the vehicle (removing and replacing the petrol cap), then drive  5 miles or so to the petrol station to actually fill it half full. Hopefully this would indicate whether it's something to do with removal of the petrol cap (doubtful) or the result of petrol entering the tank.

Edited October 16, 2017 by wizard

[Brainz006]

While your battery was likely part of the original issue (with multiple codes), your voltage (and lack of weird codes) suggests it's fine. Battery now seems like a red herring.

What you are describing sounds like purge valve. Google P0441 Cayenne and you'll see that most roads lead to replacing the PV.

Usually the hard running is immediately after filling up - - mine (CTT) would crank for a long time and then be stumbly for a minute, and then clear up. It sounds like yours is non-turbo, which may manifest differently (but similar).

As I understand the issue/system, what happens is that when you fill up, fuel gets sucked into the tank evap system and is eventually sucked into the intake (as unmetered vapors that cause the engine to run rough). The purge valve is supposed to block the vapors (closed) from being pulled into the intake at idle and low speeds and causing poor running. But when you're cruising, the PV will open and pull a vacuum on the fuel evap system. There is a sensor that measures the vacuum on the evap system. By clamping the intake hose, you will trip that sensor. If you let the car sit overnight (or keep driving) , the fuel in the evap system will evaporate and your problem will go away until you refill again.

You need to test the PV as Lewis suggests above.






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[DannyHoffman]

My car is also a turbo.

 

I sort of understand your logic of how clamping the flexible hose on the purge valve after filling the tank might not eliminate a faulty valve. If I was to clamp it prior to filling up would that tell me anything?

 

I have now pulled the purge valve pipe at the firewall end and tested it as Lewis suggested. I cannot blow or suck through it.

 

I have never had any problems starting the car.

 

The cigarette lighter volt meter arrived today so I can monitor voltage whilst driving