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Author Topic: [2.7T] lean idle trims, rich partial trims.  (Read 13084 times)
erykv1
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« on: May 01, 2016, 11:55:40 AM »

Hey all,

I've been dealing with this issue for the past month to no resolution. I've posted it on a few other forums, gotten some good suggestions, but they all lead to dead ends. Nyet & Phila_Dot have also been extremely helpful, but unfortunately I cannot seem to resolve these issues. I have had an audi tech & mercedes tech look over this car and they have no idea what is wrong either.

Background info: Performed a 6 speed swap, while the whole drivetrain was out I resealed the engine and replaced almost every hose on the car. Flashed a base tune from Daz in December and I've been dealing with wonky fuel trim values since. The car is K24 RS6'd, 3 bar map sensor, 630cc injectors, and all the stage 3 supporting mods.

Symptoms: The fuel trims read around +6% to 7% at idle, and -18% to -20% at partial in measuring blocks 032. I almost always immediately get a P1557 Positive Deviation code, so logging data is almost useless as it throws the car in limp as soon as I drive it.

I know the most common reply to these issues is to do a boost leak test. I've tested and tested this car to no avail.

Troubleshooting:
Here's what I've tried so far to bring you guys up to speed, I only used OEM parts unless otherwise noted:

  • -Tried 3 OEM hitachi mafs and 1 non OEM maf, I've tried them all and they all have wacky trims
  • -Replaced both green check valves by the intake manifold to rule out any internal leaks, checked the replacement green valves for function before installing, they are in the correct orientation as well
  • -Made sure the check valve on the brake booster hose was good
  • -Re-checked the re-built spider hose for leaks as well as check valve functionality, there is suction at the pancake valve at idle
  • -Removed the brake reservoir vacuum sensor and replaced w/ a straight fitting (this sensor was left from when the car was tiptronic)
  • -Threw on my OEM DV's just in case (as a regular pressure test will not reveal a leak here due to equalized pressures on both sides of the DVs)
  • -Replaced all o-rings on the spider hose quick connects to rule out any leaks there
  • -Checked the vacuum line running from the intake manifold to the FPR (as this would cause exactly the lean idle & rich partial trims)... lines looked great
  • -Replaced intake manifold gaskets to rule that out
  • -Replaced coolant temp sensor as I thought it may be faulty keeping the car in open loop mode
  • -Replaced the n249, as well as the combi valve it is attached to
  • -N75 lines were replaced during the rebuild, and checked with a mityvac and the lines hold vac with absolutely no bleed down.
  • -bypassed the N75, ran the car on wastegate pressure, holds pressure to 14-15 psi

Things worth noting: Everyone that has looked at my logs, has mentioned that the MAF voltage reaches almost its limit (4.5-4.6V) at only 17-18 psi.

Also here is a log (albeit in limp mode) for anyone interested: https://drive.google.com/open?id=0B6rUs76HSzcUWkFEdzB4QnM4SlE
   
At this point I'm willing to try anything (I will balance a pancake on my head and hop on one foot if it will solve my problems). I really don't want to have to drop this car off at a shop to have them troubleshoot it, but things aren't looking too good on my end.

Thanks for any advice!





« Last Edit: May 01, 2016, 04:36:11 PM by erykv1 » Logged
TijnCU
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« Reply #1 on: May 01, 2016, 12:13:25 PM »

Cheap test is to replace your fpr with some spare/known working unit. Or measure fuel pressure under vacuum/load.
Another option is to measure AFR seperately and even test the cars AFR when there is no lambda control (disconnect sensor). to rule out o2 sensor fault or calibration weirdness.
And last: verify that your maf is scaled correctly, since I cant tell from your story if there has been any mods in the ecu on that department.
Good luck!
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erykv1
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« Reply #2 on: May 01, 2016, 04:35:09 PM »

Cheap test is to replace your fpr with some spare/known working unit. Or measure fuel pressure under vacuum/load.
Another option is to measure AFR seperately and even test the cars AFR when there is no lambda control (disconnect sensor). to rule out o2 sensor fault or calibration weirdness.
And last: verify that your maf is scaled correctly, since I cant tell from your story if there has been any mods in the ecu on that department.
Good luck!

Hi TijnCU, thanks for the reply!

The FPR is indeed the original one with the car (only 110kmiles on it though). I figured if the FPR was bad, it would be lean / lean, or rich / rich in the LTFT's. The fact that it is switching between a lean condition and rich condition at idle leads me to think that it isnt? However, replacing it isnt expensive and I will definitely look into it.

The MAF scaling and MFHLM tables have been checked and sized correctly to the diameter of my MAF housing.
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nubcake
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« Reply #3 on: May 01, 2016, 04:44:36 PM »

For starters, it would be nice to figure out whether your issue is with software or hardware.

If you can get a WBO2 somewhere - check actual AFR. Same goes for fuel pressure (both idle & load).
If that's asking too much - well, back to basics. Which injectors are you running? Double-check the FPR rating. What fuel pump? What are your KRKTE/TVUB values? How does FKKVS look? KFLF?

Quote
Everyone that has looked at my logs, has mentioned that the MAF voltage reaches almost its limit (4.5-4.6V) at only 17-18 psi.

This makes me think that something's wrong with your MAF maps, it's probably overscaled? Is MLOFS zero like it should be with hitachi? How did you scale your MAF? What is the diameter of current housing? Does it have flow straighteners?

Which ECU are you running? Are you sure your definitions for it are correct?
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erykv1
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« Reply #4 on: May 01, 2016, 06:44:40 PM »

For starters, it would be nice to figure out whether your issue is with software or hardware.

If you can get a WBO2 somewhere - check actual AFR. Same goes for fuel pressure (both idle & load).
If that's asking too much - well, back to basics. Which injectors are you running? Double-check the FPR rating. What fuel pump? What are your KRKTE/TVUB values? How does FKKVS look? KFLF?

This makes me think that something's wrong with your MAF maps, it's probably overscaled? Is MLOFS zero like it should be with hitachi? How did you scale your MAF? What is the diameter of current housing? Does it have flow straighteners?

Which ECU are you running? Are you sure your definitions for it are correct?

I am running a AEM wideband, logs can be seen above. Fuel pressure is something I need to check, but I am unsure how to check under load pressure, checking idle is not a problem. Wouldn't fuel pressure issues cause misfires / idle issues? I am experiencing none of those.

KRKTE values / TVUB values are correct for the ev14 630cc's I am running. A few people have looked at the binary file and have mentioned that the MAF values are correctly scaled. I have verified that MLOF's is indeed zero. No flow straighteners, but there is at least 6 inches of straight piping before the sensor.

AFAIK the definitions are correct for the ECU.
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vwaudiguy
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« Reply #5 on: May 01, 2016, 08:34:48 PM »

but I am unsure how to check under load pressure

We usually duct tape a fuel pressure gauge to the windshield, and go for a spin.  Smiley
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nubcake
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« Reply #6 on: May 02, 2016, 04:33:18 AM »

A bit longer log would be super. Also log msdk_w please.
From this one - I don't like that ps_w is way over pvdk_w (indication of the overscaled MAF). Lambda request in the end of the log is 1.047, which is also weird.
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nyet
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« Reply #7 on: May 02, 2016, 10:58:41 AM »

A bit longer log would be super. Also log msdk_w please.
From this one - I don't like that ps_w is way over pvdk_w (indication of the overscaled MAF).

Or a DV leak...
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erykv1
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« Reply #8 on: May 02, 2016, 01:16:31 PM »

A bit longer log would be super. Also log msdk_w please.
From this one - I don't like that ps_w is way over pvdk_w (indication of the overscaled MAF). Lambda request in the end of the log is 1.047, which is also weird.

I will try to get an updated log as soon as I can.

Or a DV leak...

I put on factory DV's and drove around, the trims shot back up with my current 034 DV's.
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erykv1
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« Reply #9 on: May 03, 2016, 11:53:15 AM »

two questions:

- If I unplug the MAF, will the fuel trims still adapt?
- Will a FPR going out cause these issues (lean at idle, then rich at partial?) I have zero idle problems / misfires.
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TijnCU
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« Reply #10 on: May 03, 2016, 12:23:43 PM »

You have a wideband o2, so why dont you just test it? I would pull the maf plug off, drive around for a bit and observe standalone o2 and ecu fuel trims. Easy enough to find out... You probably will be in limp mode, so not much boost  Huh
The only correct way to diagnose your fpr is to stick a pressure gauge in the rail. I don't know if it can cause these issues, but when you are troubleshooting you have to eliminate options. Assumption is the mother of all fuckups  Tongue

I put on factory DV's and drove around, the trims shot back up with my current 034 DV's.
What does this mean? You observe no difference in fuel trims between those dv's, or you do? The way I read it, it seems you write the trims are worse with the 034 dv's. You can test DV's by applying vacuum to the top and it should remain opened. The closed state can be tested in a normal intake pressure test, or by applying pressure to the dv's individually.
« Last Edit: May 03, 2016, 12:30:40 PM by TijnCU » Logged

erykv1
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« Reply #11 on: May 03, 2016, 01:21:17 PM »

You have a wideband o2, so why dont you just test it? I would pull the maf plug off, drive around for a bit and observe standalone o2 and ecu fuel trims. Easy enough to find out... You probably will be in limp mode, so not much boost  Huh
The only correct way to diagnose your fpr is to stick a pressure gauge in the rail. I don't know if it can cause these issues, but when you are troubleshooting you have to eliminate options. Assumption is the mother of all fuckups  Tongue
What does this mean? You observe no difference in fuel trims between those dv's, or you do? The way I read it, it seems you write the trims are worse with the 034 dv's. You can test DV's by applying vacuum to the top and it should remain opened. The closed state can be tested in a normal intake pressure test, or by applying pressure to the dv's individually.


I've done the unplugging MAF part, but it seems like the LTFT's arent registering with it unplugged. Hence me asking the question. My car is almost always in limp mode due to the positive deviation code that pops up. I am pretty sure that is tune related.

When I put on the factory DV's, there was no difference in the fuel trims as with the 034 DV's. Sorry for not being clear.

Unless there is a huge hole in my IC making the leak silent, I don't have much left to check. At least the FPR is cheap to replace. A gauge almost costs the same, lol.

I will report back. I'm going to give this another week before I accept defeat and let a shop take care of it.
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TijnCU
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« Reply #12 on: May 03, 2016, 01:43:53 PM »

It's not important if there is no ltft, you can monitor the afr on your wideband. Just make sure it does not go super lean.. Its only for verification how the ecu responds to the (missing) sensors...
If the hardware is ruled out you can try to flash a new base file with only fueling mods to figure out what the maf does. If you do bring the car away with custom software, the garage has to be able to tune (in case there is a mistake in the flash...) so I would choose a tuner company with a dyno.
This just came to mind:
Have you tried to do a transparent vac line from the manifold to the fpr? They do leak sometimes, i've had it myself. It will push out fuel through the diaphragm.
« Last Edit: May 03, 2016, 01:51:38 PM by TijnCU » Logged

erykv1
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« Reply #13 on: May 03, 2016, 06:20:17 PM »

It's not important if there is no ltft, you can monitor the afr on your wideband. Just make sure it does not go super lean.. Its only for verification how the ecu responds to the (missing) sensors...
If the hardware is ruled out you can try to flash a new base file with only fueling mods to figure out what the maf does. If you do bring the car away with custom software, the garage has to be able to tune (in case there is a mistake in the flash...) so I would choose a tuner company with a dyno.
This just came to mind:
Have you tried to do a transparent vac line from the manifold to the fpr? They do leak sometimes, i've had it myself. It will push out fuel through the diaphragm.

I am currently searching for a proper method to test fuel pressure as there is no schrader valve anywhere that I can tap into to use those fuel pressure testing kits.

I've checked the FPR line and it seems dry when I pull it off, a clear line isn't a bad idea though!

I have noticed however, that my dipstick smells really strong of fuel? Seems like there is a 50/50 opinion on if that is normal or not.
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nubcake
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« Reply #14 on: May 03, 2016, 07:16:01 PM »

I have noticed however, that my dipstick smells really strong of fuel? Seems like there is a 50/50 opinion on if that is normal or not.

No wonder. According to fuel trims and to the log you posted (and assuming your WBO calibration is correct), you're flooding the engine with petrol. With AFRs deep into 10s.

I'd just ignore the "lean idle" for now and concentrate on the "too rich under load". FPR shouldn't do that. I still -strongly- suspect that it's MAF related.
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