[AndyW]

Originally Posted by lightmanek

Yes, sensor was knocked out during DP installation.

Only codes I have are efficiency shadow codes related to high flow cats, no O2 failure codes.

[MHD Tuning]

Try to reset the transmission adaptations (and follow the relearning process).

[AndyW]

Originally Posted by MHD Tuning

Try to reset the transmission adaptations (and follow the relearning process).

Thx Martial. I actually went down that path a few months back, including a transmission flash back to stock and adaptation relearn process. Then I realized it will do it in Park in the garage holding the throttle at 2-4%. Transmission can't affect the engine in Park, can it? Maybe that's a bad assumption?

[V8bait]

Looks like a vacuum leak to me. And checking vacuum at the canister doesn't mean anything that's tied to the vacuum pump. When was your last walnut blasting and did the symptoms come about around that time? Those O rings are nice failure points. Also the nipple for the line to the DV's is prone to damage during blasts when the manifold is removed.

[AndyW]

Originally Posted by V8bait

Looks like a vacuum leak to me. And checking vacuum at the canister doesn't mean anything that's tied to the vacuum pump. When was your last walnut blasting and did the symptoms come about around that time? Those O rings are nice failure points. Also the nipple for the line to the DV's is prone to damage during blasts when the manifold is removed.

I thought so too, at first. Been about 25k since walnut blasting. Gaskets replaced at that time. Symptoms did not start at that time. Have had intake manifold off and back on since then. Power runs indicate no boost leak. I know that nipple and it is good. The main thing that makes me discount a vacuum leak is that it has no issues at idle, where those problems typically manifest.

[V8bait]

Originally Posted by AndyW

I thought so too, at first. Been about 25k since walnut blasting. Gaskets replaced at that time. Symptoms did not start at that time. Have had intake manifold off and back on since then. Power runs indicate no boost leak. I know that nipple and it is good. The main thing that makes me discount a vacuum leak is that it has no issues at idle, where those problems typically manifest.

Well the afr goes lean on both banks and trims max out like it's getting extra air. Maybe O2 plugs are swapped? I doubt it's one sensor since both are measuring an afr swing and reacting the same.

[AndyW]

Originally Posted by V8bait

Well the afr goes lean on both banks and trims max out like it's getting extra air. Maybe O2 plugs are swapped? I doubt it's one sensor since both are measuring an afr swing and reacting the same.

Just replaced both WB O2 sensors (as in today - and I double checked the connections). Car seems smoother and symptoms didn't appear on a short drive but I can cause the oscillation in the driveway. Seems smaller, tho'. Guess it can't hurt to do another vacuum test.

[AndyW]

Appreciate everyone throwing out ideas...it helps me relook at stuff in a different way!

[lightmanek]

Try doing octane adaptation reset after O2 replacement. Needs good few miles to relearn but it might help that bit more.

[AndyW]

Originally Posted by lightmanek

Try doing octane adaptation reset after O2 replacement. Needs good few miles to relearn but it might help that bit more.

You are a mind-reader...I was just about to ask what that reset did!

[FamilyManTrackSedan]

+1 on throttle body and tps

[AndyW]

O2 sensors definitely did not fix it.

[onefireball]

I hope you can get this figured out. I have the same issue with mine.
08 6mt FBO.
It really got bad after installing the VRSF exhaust a few months ago.

Can not stand to use the cruise, the surging is too bad at highway speeds.
I have tried all the normal software stuff with JB4, MHD, resetting adaptations, etc... no help.

If I had not just installed m3 suspension bits and Ohlins coilovers I would get rid of it..

[galahad05]

Noticed any excessive oil consumption? PCV valve....

[AndyW]

Originally Posted by galahad05

Noticed any excessive oil consumption? PCV valve....

Nope. And PCV is RB.

[galahad05]

Okay (still reaching for straws here). Have you tried different gas? What octane?

[galahad05]

So I broke out my Bendley on the 3 series, to see if I can throw some info in here, in case it can give someone ideas to explore.



It says:
3 Series turbo engine utilizes a calculated air mass system. This calculation makes use of the following signals:
- VANOS setting (load acquisition)
- Throttle setting
- Intake air temperature (air density correction)
- Engine temperature (air density correction)
- Engine speed (cylinder charge)
- Intake manifold pressure (throttle correction)
- Ambient pressure (air density, altitude correction)

The calculated air mass is adjusted with the oxygen sensor signal (mixture ratio) and injector timing and corrected if necessary.





In addition, this is what it says about the N54's throttle assembly:
<installation of throttle assembly>
--Installation is reverse of removal.
--Reattach throttle assembly connector with care.
CAUTION--it is possible to twist the connector before plugging it in. This can cause damage to the harness and connector.
--...

[galahad05]

Also, how old is your battery? A buddy of mine with an '08 was getting pissed off at his car because it was having ever increasing drivability issues, with no codes thrown. Started off with uneven power at light throttle.....

Ended up being a slowly fading battery. He replaced it a couple months back, car runs perfect now. He's back in love with his car.

[onefireball]

The Battery is a good idea.
I know mine is coming up on 5 yeays old.
Not sure about OP, but I will try that for sure.

Thanks!

[AndyW]

Battery...yeah, mines over 5 years old. How that could cause this is beyond me, tho...

[galahad05]

Originally Posted by AndyW

Battery...yeah, mines over 5 years old. How that could cause this is beyond me, tho...

Here's one hypothetical scenario: pretty much every signal from the analog sensors in the car, like the throttle butterfly and the accelerator pedal, have to be converted to digital numbers in the ECU. Pretty much all analog to digital converters rely on a reference voltage to compare against. If that reference voltage were out of spec just a little bit.....

[AndyW]

For reference, here's a log with MHD 7.1 stg 2+ 91 Oct.

http://www.datazap.me/u/andyw/mhd-71...10-11-12-13-24

Doesn't appear to have a boost leak. Only cylinder 4 has minor corrections. Fuel pressure OK. Only thing I noticed this time is that bank 1 lambda lags bank 2 slightly on throttle-off. Indicates over fueling not excess air. So injector leaking? Would be surprised, as I have replaced all Injectors and while they were used, I tested all of them. Not sure if this would cause my issue, either. Any thoughts on how much difference in lambda recovery is too much? In the meantime, I'll check spark plugs for signs of a leaky injector. Last time I checked, they were all dry.