Code: Too lean at idle

[mtroxel]

Got a CEL a couple days ago, took note and cleared it. Now it's back. Same codes:

Address 01: Engine Labels: 06F-907-115-AXX.clb
Control Module Part Number: 8E0 910 115 M HW: 8E0 907 115 D
Component and/or Version: 2.0l R4/4V TFSI 0060
Software Coding: 0104010A190F0120
Work Shop Code: WSC 69123 444 131735
VCID: 2B553CC58AC6E966F4-807E
2 Faults Found:

008583 - Bank 1; System too Lean at Idle
P2187 - 004 - - MIL ON
Freeze Frame:
Fault Status: 11100100
Fault Priority: 0
Fault Frequency: 1
Reset counter: 255
Mileage: 166870 km
Time Indication: 0

Freeze Frame:
RPM: 783 /min
Load: 19.6 %
Speed: 0.0 km/h
Temperature: 81.0°C
Temperature: 9.0°C
Absolute Pres.: 960.0 mbar
Voltage: 13.716 V

001287 - Idle Control System RPM
P0507 - 001 - Higher than Expected. - Intermittent
Freeze Frame:
Fault Status: 00100001
Fault Priority: 0
Fault Frequency: 3
Reset counter: 255
Mileage: 166872 km
Time Indication: 0

Freeze Frame:
RPM: 938 /min
Load: 14.1 %
Speed: 0.0 km/h
Temperature: 78.0°C
Temperature: 10.0°C
Absolute Pres.: 960.0 mbar
Voltage: 13.843 V

The first happened 2 KM before the 2nd, though they sure seem related don't they?

I'm looking at these RossTech pages on both:

http://wiki.ross-tech.com/wiki/index...9/P2187/008583
http://wiki.ross-tech.com/wiki/index...1/P0507/001287

I'll test N80 tomorrow, and I believe there are some resistance tests on the MAF in Bentley. What else should I chase?

[allstock]

Lean is not good. Richer is the better of two polars. I'd be ruling out vacuum leaks first. If your n80 was on its way out you'd have a history of persistent evap code. MAF on our cars are pretty robust and you'd get a code there too most likely. I wonder what your fuel trims look like.

[mtroxel]

I wonder what your fuel trims look like.

Thanks for the response. It’s -3˚ right now, but sooner or later I’ll get up the courage to go sit in the garage with my bare fingers on a keyboard with the car idling and the door open. I might do a 2nd gear WOT graph on it too.

[mtroxel]

OK, I'm out of my depth. Started the car, hasn't run for about 14 hours, sat all night in an attached garage with the temp somewhere in the teens. Cold motor at idle, I get no STFT adjustment from Group 33. Are the O2's just too cold to give a reading? Shouldn't they be flipping between rich and lean...constantly? It's not worth attaching a graph, the Lamda in Group 33 stays at 0.0% and does not move.

Also, I cleared codes yesterday, so the LTFT probably only has about 4 driving cycles on it.

[allstock]

That's normal. Lambda control doesn't start registering until the 30-40 Celsius. Voltage is alright. Idle is very high, should be in the decimals near zero below 1.

[mtroxel]

Did some testing today. Got it warmed up, did a couple WOT runs in 2nd gear. Both times I saw between 185-190 g/s out of the MAF. So it's probably not the problem. However, at idle these are my fuel trims.



If I'm reading this right, the LTFT is correcting for a lean condition. Then on top of that, the STFT is also correcting for more lean conditions. Pretty much means an air leak doesn't it?

So if I spray starter spray all around my motor, I don't see the trim change much unless I completely soak the area circled in red. I mean SOAK! And even then the STFT is only dropping to about -1% with the LTFT up at +6-7%! So either I have a leak in the aftermarket PCV valve there, or in something underneath that isn't affected until it's dripping off the PCV valve. Am I looking at this right?



EDIT: Oh, and if I wife out the LTFT by clearing codes while the motor is idling, it almost stalls.

[saizero]

Check your LPFP duty cycle. If it at 55% or higher, your fuel pump might be on its way out or you need to change fuel filter. Insufficent fuel supply to the HPFP might be the cause of your lean codes.

[allstock]

Check your LPFP duty cycle. If it at 55% or higher, your fuel pump might be on its way out or you need to change fuel filter. Insufficent fuel supply to the HPFP might be the cause of your lean codes.

55 percent is actually pretty good and normal. Consistent high seventies and up is an indication the lpfp is on its last leg.

[saizero]

Allstock is correct, ideally the closer to 50% at idle the better, but once you're in hit 60 you're in the grey area, and in 70% it's on it's way out.

[mtroxel]

Check your LPFP duty cycle. If it at 55% or higher, your fuel pump might be on its way out or you need to change fuel filter. Insufficent fuel supply to the HPFP might be the cause of your lean codes.

Good idea, here's mine at idle:



So it's an air leak, not a fuel delivery problem. So I fired up a Hoyo de Monterry Excalibur Classic IV (with the claro wrapper), we all know that's the best kind of leak detector. I can't get anything to suck in smoke, even from a nice cigar like that! But, I sure hear a lot of air moving in that PCV valve. I turn off the engine and for a few seconds after I hear air seeping through that valve. Is it possible to have an internal leak through one of those check valves in there?

[saizero]

You could try a finding a leak with a propellant like carb clean, while monitoring your STFT. When it goes rich you've found the leak. Obviously use caution and common sense when using the propellant around a hot engine.

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[MrBigglesworth]

To be honest your fuel trims aren't that bad.

I have a trim that hovers just above 10% so out of spec and it's a pain trying to diagnose it!

If your boost vs request, lambda vs request, high pressure vs request and low pressure vs request are fine then maybe best just 'monitored' for now rather than losing too much sleep.

Are you mapped - 186g/s on MAF is quite high.

[mtroxel]

You could try a finding a leak with a propellant like carb clean, while monitoring your STFT. When it goes rich you've found the leak. Obviously use caution and common sense when using the propellant around a hot engine.

Did that yesterday, and again today. Used starting fluid, and I can make the STFT go leaner when I spray in the area I circled in red above. So today I just gave up and pried that PCV apart. Not sure how this works, but I guarantee you the torn diaphragm isn't doing me any favors. Is that letting boosted air into my intake and making my "lean idle" codes and my "intake air leak" codes too? I'll know tomorrow when I get a new one from the dealer. I glued it back together and screwed it back on.



That's the Vaico one I saved $15 on 8 months ago. Won't do that again.

To be honest your fuel trims aren't that bad.

But I've been getting a CEL for lean at idle several times now. And now its accompanied by an intake air leak CEL also.

Are you mapped - 186g/s on MAF is quite high.

I thought the same thing, but I'm bone stock in every way. On one of my WOT runs I hit 190 g/s.

[allstock]

To be honest your fuel trims aren't that bad.

I have a trim that hovers just above 10% so out of spec and it's a pain trying to diagnose it!

If your boost vs request, lambda vs request, high pressure vs request and low pressure vs request are fine then maybe best just 'monitored' for now rather than losing too much sleep.

Are you mapped - 186g/s on MAF is quite high.

His stft is high and should be close to zero even on a car with 100k.

His lambda control is high. The damn ecu is telling him he is running too lean. Do you know what happens to a motor running excessively lean?
To me that sucks and is lackluster to take the head in the sand approach. Of course it doesn't matter if you don't give crapp.

His g/s is fine specifically when it was registered while floored - let alone second gear. Third and fourth gear wot is sufficient when logging wot.

That's the Vaico one I saved $15 on 8 months ago. Won't do that again.

You buy shitt - you get shitt more often than not. "OEM" is bullshitt, get the Audi labeled part or make damn sure that the OE manufacturer makes that specific part FOR Audi and save money there.

Hope your trims drop. Good luck

[mtroxel]

Do you know what happens to a motor running excessively lean?

Ummmmm...burnt pistons? Yea even with the LTFT pushing things richer, the STFT is still never getting to stoichiometric. Not even close. Something has changed in the last few days, and I'm betting it's that torn diaphragm.

You buy shitt - you get shitt more often than not. "OEM" is bullshitt, get the Audi labeled part or make damn sure that the OE manufacturer makes that specific part FOR Audi and save money there.

Every now and then I have to re-learn that one.

[MrBigglesworth]

I thought the same thing, but I'm bone stock in every way. On one of my WOT runs I hit 190 g/s.

Have you got a stock air intake?

If under vacuum your pcv did have a path for excess air flow then then it could suck in air and cause you to go lean at idle.

Aftermarket consumable parts seem rarely worth the saving in my experience.

[mtroxel]

Have you got a stock air intake?

Bone stock. Some of these guys running big turbos might need to find more air. But air intake systems are generally pretty overrated.

[MrBigglesworth]

Bone stock. Some of these guys running big turbos might need to find more air. But air intake systems are generally pretty overrated.

I am still surprised at your MAF reading - the logs/graphs I have seen for stock 2.0T tend to get to high 150s/low 160s with not a huge difference between 2nd and 3rd gear (around +5g/s).

It's also interesting that your learned long term values for idle/additive are at c.6%, but you are triggering a fault code which I thought means the fueling adjustment is hitting something like +25%. One thing that could help is if you could capture this on a live data log to find out when exactly and what you were doing when the fueling adjustment jumped that much (logging rpm, throttle, misfires, etc).

[mtroxel]

$60 at the dealer and it's good as new. I took apart that bad PCV again and saw what's happening. The back side of that diaphragm is purposely ventilated to the atmosphere. If you trap air there, diaphragm's not going to move. So if there's a cut in the diaphragm, you get outside air. Now my trims look like this:



STFT toggles between - and +, just like it should.

[MrBigglesworth]

Glad you got yours sorted!