Lopey Idle and intake pops on a cold start

[tristancboyd@gmail.com]

Hey all, here's a video of the problem I'm having.  It was happening when I was getting a MAF sensor code.  I've replaced it, reset the codes, driven two tanks and am still having this issue.  Other than this issue, the car runs great and is getting 24-26mpg average.

 

2002 Boxster S

6-Speed

 

https://www.youtube.com/watch?v=zFVuFkICEPk

Edited December 19, 2015 by tristancboyd@gmail.com

[JFP in PA]

What codes were you/are you getting?

[tristancboyd@gmail.com]

I can't remember now exactly. I believe the description had something to due with low voltage or something with the MAF.  Low-something.  helpful, I know but I cleared it several weeks ago.

 

Also, tonight I noticed that where I thought it was running fine, there seems to be a dip or hesitation between 2000-2700ish RPMS.

 

Still no codes

[JFP in PA]

Rescan the vehicle, paying attention to both MAF actual values and fuel trims, then report back what you have found.

[tristancboyd@gmail.com]

This was off of a warm start, I figured it would be a useful reference.  as soon as I can get cold start data, I'll share it as well.

 

The spike is a rev

 

 

 

[JFP in PA]

Sorry, but I am not familiar with the reporting values diagnostics tool you are using; Porsche systems fuel trims are rated according to reading your FRA (load) and TRA (idle) adaptation values for each bank, with the FRA range limits on adaptation for both banks are Rich: 1.25 and Lean: 0.75 (For example, an "in spec" "long term" FRA trim would be around 1.0 +/- 0.1 and an in spec "idle range" fuel trim would be in the range 0.00 +/- .2).  Porsche also set the MAF values at 10-20 Kg/Hr. at idle, and 30-60 Kg/Hr. at 3K RPM (no load).  If your tool is reading in gram/second, 6.8 gram/sec at idle would equate to 24.5 Kg/Hr., which would be a high air mass at idle (a possible lean condition).  I also note that your secondary air system is reading "incomplete", which could be related to the problem you are seeing.

 

If at all possible, I would suggest getting the car rescanned with a Porsche specific tool (PST II, PIWIS, or Durametric system).

[tristancboyd@gmail.com]

Sorry, but I am not familiar with the reporting values diagnostics tool you are using; Porsche systems fuel trims are rated according to reading your FRA (load) and TRA (idle) adaptation values for each bank, with the FRA range limits on adaptation for both banks are Rich: 1.25 and Lean: 0.75 (For example, an "in spec" "long term" FRA trim would be around 1.0 +/- 0.1 and an in spec "idle range" fuel trim would be in the range 0.00 +/- .2).  Porsche also set the MAF values at 10-20 Kg/Hr. at idle, and 30-60 Kg/Hr. at 3K RPM (no load).  If your tool is reading in gram/second, 6.8 gram/sec at idle would equate to 24.5 Kg/Hr., which would be a high air mass at idle (a possible lean condition).  I also note that your secondary air system is reading "incomplete", which could be related to the problem you are seeing.

 

If at all possible, I would suggest getting the car rescanned with a Porsche specific tool (PST II, PIWIS, or Durametric system).

 

 

I don't have access to one of those but using this information, I'll see if I can't clean up the read-outs to something a little more useful for this troubleshooting.  And also, I appreciate your help.  Thank you.

[Ahsai]

Agree with John your MAF reading is way too high at warm idle. It should be around 4g/s at idle speed ~680-700rpm.

What kind of MAF sensor you put in and are you sure it's the right one for your model?

It would be useful to log the following (at idle) in Torque during cold start and after fully warmed up:

- short term fuel trims on both banks

- long term fuel trims on both banks

- Bank 1 O2 sensor 1 voltage

- Bank 1 O2 sensor 2 voltage

- Bank 2 O2 sensor 1 voltage

- Bank 2 O2 sensor 2 voltage

- MAF

- coolant temp

- rpm

[Ahsai]

Btw, any intake mods and have you tried driving the car with the MAF unplugged?

From your data, looks like the MAF is over reading the intake air flow at idle so the DME has to pull fuel like crazy (negative short term fuel trim) on both banks at idle. To compensate, the DME has to add back fuel when under load hence the positive long term fuel trims.

[tristancboyd@gmail.com]

Agree with John your MAF reading is way too high at warm idle. It should be around 4g/s at idle speed ~680-700rpm.

What kind of MAF sensor you put in and are you sure it's the right one for your model?

It would be useful to log the following (at idle) in Torque during cold start and after fully warmed up:

- short term fuel trims on both banks

- long term fuel trims on both banks

- Bank 1 O2 sensor 1 voltage

- Bank 1 O2 sensor 2 voltage

- Bank 2 O2 sensor 1 voltage

- Bank 2 O2 sensor 2 voltage

- MAF

- coolant temp

- rpm

 

I set these up in my app almost exact but messed up the logging, I'm going to try again in the morning.

 

The only Mod I have is a desnorkle, everything else is otherwise stock.

 

I put a few screen shots below

 

The MAF I ordered is this one

 

 

[Ahsai]

STFT 1 appears twice and LTFT1 is missing. The two "F/T..." are not needed. We still need the O2 sensor voltage from all 4 O2 sensors. Not clear to me but is the MAF by Bosch? If not, I think it's a strong suspect.

Not familiar with the desnorkle mod but can it be reversed?

[tristancboyd@gmail.com]

STFT 1 appears twice and LTFT1 is missing. The two "F/T..." are not needed. We still need the O2 sensor voltage from all 4 O2 sensors. Not clear to me but is the MAF by Bosch? If not, I think it's a strong suspect.

Not familiar with the desnorkle mod but can it be reversed?

I missed that I had repeated read outs.  I put it up in a hurry.  I'll set up the read out dashboard now and make sure its good to go for the morning.  The MAF is probably not Bosch, I do not remember seeing anything that would link it to Bosch.

 

The desnorkle is more of a sound modification than anything.  It's removing a sound baffle from the intake tube in the side of the car.  

[Ahsai]

I don't have the PET handy but maybe John can shed some light on the correct p/n for your year and model. If the MAF is $50 from ebay, I would not trust it. The Bosch ones are about $250 each and those should be good.

You can still try to drive your car with the MAF unplugged and see if that makes a difference, maybe after you finished logging the data with the curret MAF.

[JFP in PA]

I come up with at 996-606-124-00 as the correct part for your car.  Should retail somewhere between $250-275, or list for about $600 at a Porsche dealer.

[mikefocke]

The desnorkle itself should not cause any CELs because it is upstream of the air filter and MAF.  It just changes the sound.

 

But, in doing it, connections that could cause a CEL could have been disturbed.

 

Get the CEL diagnosed and report the Pnnnn values. Many car parts places can do it for free and the emissions control codes are readable with basic code readers.  The Porsche specific diagnostic tools such as JFP suggests may be needed after you see the basic reported code and post it here and someone reads the manual for your specific ECU revision and tells you the typical causes that cause that CEL and codes to be displayed.

 

Think of the diagnosis as moving down from CEL on the dashboard to codes via a code reader and then to more specific engine operating parameters via the specialized Porsche tools.

 

But I'd take the basic and cheap steps first.

 

Also, when you post, tell us what on the car, engine, exhaust is not perfectly stock. And what has been changed since the car ran without problems.

 

I might even put the old MAF in as I too suspect the new MAF and we'd get better diagnosis with the part in there whose operating characteristics match what the software in the ECU expects.

Edited December 21, 2015 by mikefocke

[tristancboyd@gmail.com]

I think I got some really good data today and I have it uploaded to the torque web viewer.  It can be seen publicly but putting my torque ID in, no password required for viewing.  I'd just snip it and paste but then you cant see the specific values as you mouse over them.  I also have the  CSV values for the logs if someone is able to view those.  Oddly enough, it behaved today at idle.  Still a little hesitation starting around 2200.

 

It's the 3.2, 6-speed.  

Other than the desnorkle, its completely stock

 

http://view.torque-bhp.com/

 

Device ID: 990005434631165

[Ahsai]

I saw two issues with your engine:

 

1) Bank 1 sensor 2 (red line) too slow to respond. That's likely why your SAI readiness flag is not set. You can see engine starts at ~150s and close loop is achieved at ~190s and Bank 1 sensor 2 lags behind Bank 2 sensor 2 when detecting the extra O2 introduced by the SAI pump (excessive O2 => low voltage).

 

 

2) MAF reading / fuel trims are erratic. Long term fuel trims (on both banks) drifted from +15% to -10% between your first drive to your last drive. I saw that when idle, sometimes the MAF reading is in spec but a lot of time it's not. Suggest you remove the MAF, reset the DME and re-log.

Edited December 22, 2015 by Ahsai

[tristancboyd@gmail.com]

Between yesterday and today, the idle has not acted up once.  Today there was not any hesitiation to be found.  I decided to look at the system status again, and everything has completed.  I'm debating on whether to pursue this further or let it be and hope it doesn't act up again.  You guys are a wealth of information!

 

[Ahsai]

The easiest is to check the LTFT when you feel the engine is not smooth (either idle or under load). Those should be +/- 10%.

 

If the engine is smooth, I would just keep monitoring the fuel trims and CEL and do nothing yet.

[Ahsai]

BTW, cleaning the throttle body will help smooth out the idle too if it's dirty.

[tristancboyd@gmail.com]

Thank you all very much.  I will continue to monitor for a bit.  If it continues to behave without issue, I'll mark this solved.  The feedback between y'all has been so informative and helpful just in learning a few things is why I decided to contribute to this forum.

[tristancboyd@gmail.com]

So I'm back.  I haven't really noticed anything lately but it's also been unusually and record-breaking warm here.  

 

I went out before work this evening and started the car to let it warm up before leaving (I wanted heat!!!)  After about two minutes I went back outside to let my dogs out and didn't hear the car running.  The engine stopped.  I started it back up, a little lopey, no CEL but it settled and I went back in.  About two minutes later, I heard the idle start to get a little erratic and lopey again and then the engine quit again.  I went out and started it a third time, gave it a few revs and held some small revs for a few seconds.  This time it stayed running but I shot some video for you more knowledgeable folk.  

 

It was roughly 35F outside and the car had not been driven since the day before.  

 

Still no CEL and once it was warm, it ran like a scared cat, zero issues.

 

https://www.youtube.com/watch?v=N2M1U3IKcTc

Edited January 6, 2016 by tristancboyd@gmail.com

[JFP in PA]

So I'm back.  I haven't really noticed anything lately but it's also been unusually and record-breaking warm here.  

 

I went out before work this evening and started the car to let it warm up before leaving (I wanted heat!!!)  After about two minutes I went back outside to let my dogs out and didn't hear the car running.  The engine stopped.  I started it back up, a little lopey, no CEL but it settled and I went back in.  About two minutes later, I heard the idle start to get a little erratic and lopey again and then the engine quit again.  I went out and started it a third time, gave it a few revs and held some small revs for a few seconds.  This time it stayed running but I shot some video for you more knowledgeable folk.  

 

It was roughly 35F outside and the car had not been driven since the day before.  

 

Still no CEL and once it was warm, it ran like a scared cat, zero issues.

 

https://www.youtube.com/watch?v=N2M1U3IKcTc

 

 

Sometimes, when the MAF in these cars is starting to age out or is dirty, you will get the kinds of issues you describe.  I would pull the MAF and thoroughly clean it with an appropriate cleaner like CRC's, then reinstall it and see if the situation improves.  If it does not, I would scan the MAF PID's at idle and 2K RPM; if the values of the MAF are all out high, or even near the high end of the range, your MAF is aging out and needs to be replaced.

[tristancboyd@gmail.com]

It's been a busy week or two with my four year old going to daycare/preschool for the first time ever and getting adjusted to new schedules.  I do have somewhat of an update, but no resolution.  

 

The idle issue has correlated with showing its ugly face with the car not being driven for a couple of days or longer.  I've also noticed that the car turns over noticeably slower, but not completely weak and the lights in the car seem to have a bit of a pulse for a few minutes.  This has me wondering if perhaps the battery is beginning to fail and properly supply the vehicle with the required voltage and current needed to operate properly until the alternator is able to catch it back up.

[Ahsai]

What's the voltmeter reading at

1),cold start

2) driving with low beam and a/c ON

If the headlight flickers, you definitely have a problem with your battery or charging system.