P code expert?? What's the trim "system"?

[kevinkay]

Could Chain tensioner cause P1191 error?

Only noticed 2 times in last 50 or so start ups
COLD morning, idle sounds fine, start to accelerate and move - chattering sound, lasting only about 30 seconds. by the time I pull over, lift the hood, its gone.
First figuring its an old engine, cold thick oil and it was lifters rattling. Read others suspect this same chatter as chain tensioner?? Can chain tensioner skew DME to give me "rich" in one bank??

THANKS!

[kevinkay]

another clue??
I pulled the Air Distribution Piece that sits on the intake manifold - part of CCV system. A little bit of "mayo", but when I sprayed it out with compressed air WATER came out, including the top return? pipe.
I ordered a new CCV system. I plan to pull out, up to, and including the throttle body, clean and check for leaks and since it was noted to me that the CCV system can influence just one bank - I will replace it. I contemplated on the the "traditional PVC" cheat, but I would like to keep the BMW original to the engineers.

THANKS

[btrvalik]

I have a P1092 - but the car runs great. This weekend I did plugs, primary O2 and cleaned the MAF, but the code came back. My bank1 LTtrim runs about 7% and bank 2 runs between 7.8 and 8.5%. the ST trims bounce around while driving from +12 to -20. An indy shop did a smoke test, found no problem but said I need a new MAF. My CCV is still original (109K) but it doesn't seem to have excessive vacuum at the cap. Would like to hold off on CCV replacement till spring.

[kevinkay]

I am still searching for my issue.....
Did'nt get a chance to work on my new CCV replacement yet.
But I re-smoked my intake and valve cover - no leaks

assuming you cleaned your MAF? (get MAF cleaner at auto zone).

UPALLNIGHT pointed out this BMW service bulletin, - if your year is 03
http://www.bmwmotorsports.org/pdf/misc/120704.pdf

From my research: (none worked for me)
Many found there issue with the very common rip at the accordion turn of the Throttle Body boot -https://www.fcpeuro.com/products/bmw-air-mass-meter-boot-x5-13541440102
The Idle control valve is dirty
Gas cap not tight
Injector leaky
DISA issues

[upallnight]

Originally Posted by btrvalik

I have a P1093 also - but the car runs great. This weekend I did plugs, primary O2 and cleaned the MAF, but the code came back. My bank1 LTtrim runs about 7% and bank 2 runs between 7.8 and 8.5%. the ST trims bounce around while driving from +12 to -20. An indy shop did a smoke test, found no problem but said I need a new MAF. My CCV is still original (109K) but it doesn't seem to have excessive vacuum at the cap. Would like to hold off on CCV replacement till spring.

Check the ICV (Idle Control Valve). If it is sticking and not rattling when you shake it you can try to clean it but I would just replace it.

[btrvalik]

definitely need to do the CCV, ICV, fuel filter, etc - just would like to wait till spring. From the data I pulled, the MAF seems to respond perfectly with the RPM – sure seems to be measuring the airflow properly.

[btrvalik]

@Kevin, how long / miles have you had this code? My car runs perfectly but I don't want to ignore the code for too long and have something else fail - cats. etc

[kevinkay]

My code goes off and on (mostly on) since Nov, about 2500 miles. My car is also running perfect.

YES, I also am conserned about the cat having to deal with that extra fuel. And HATE seeing that "service" light. I am just less motivated to be under the hood in the cold...

[btrvalik]

As a bit of an experiment, I decided to scan / log my wife's CX-9 to get a better understanding of how a car that doesn't have a code reacts - perhaps a bit apples and oranges, but the basics of fuel and emissions controls seems to be fairly generic - oxygen sensors magnitudes seem to differ a bit between manufacture. Most of the reading see fairly similar to my X5 - for example if I plot MAF / RPM, the plots have the same pattern. The one that jumps out is long-term fuel trim. On my X5 the LT fuel trim will only change once every 10+ min. On the CX-9, it's changing every 20 sec or so.

According to a reference I found on the web:

The PCM’s definition of “short-term” is milliseconds, it acts incrementally, adding or subtracting fuel in small increments in an effort to hit the stoichiometric target.

the PCM is watching what’s happening in response to the changes in STFT. If STFT adds, for example, 3 percent fuel to the baseline and this makes the oxygen sensors happy, the PCM concludes that it ought to adjust the baseline. So it changes the “long term fuel trim” (LTFT). “Long term” is between 30 seconds and a minute. This creates a new baseline.

Based on the above, it would seem my LTFT is changing too slowly - up without knowing what is "normal" it's hard to tell.

@Kevin, Have you tried logging your LTFT? I'm using the Torque App and a BT OBDII which seems to work well.

[80stech]

Your on the right track but you guys need to introduce a variable to get the trim to make a change and then observe how it reacts.