Constant Lean Condition on Banks 1 & 2 [Archive] - Bimmerfest - BMW Forums

: Constant Lean Condition on Banks 1 & 2

09-15-2012, 06:40 PM
Hi all,

I'm hoping I might hear from a helpful soul or two on my ongoing issue. About a month ago, I had my local dealer replace my vacuum pump and change the spark plugs. The vehicle was at 97,000 miles, so both were normal wear and tear maintenance. About four days later, my Service Engine light came on. Went to Autozone and they showed the codes for lean condition on both banks. I went back to the dealer and they found that the crankcase vent valves were chewed up and "guaranteed" me that this was causing the vaccum leak and I had them replaced. Drove about 40 miles and the SES light came on again. Back to the dealer and this time they diagnosed about every gasket and seal needed replacing to the tune of $3800.

Figured it was time for a second opinion so I went to my local reputable indy that I had done some work with before. They ran the codes, did a smoke test, and a fuel system pressure test. According to the shop, the smoke test was negative so no vacuum leak. They also said they ruled out O2 sensor problems. The fuel system was putting out about 60% of standard pressure at cruise.

So we decided to replace the fuel pump and filter and add a can of BG44K. That was yesterday. Also, before going in for the new pump and filter, I changed the air filter and cleaned the MAF sensor.

The car is driving noticably better and I saw an immediate return to my former MPG that I was getting before starting the work. The car runs better, smoother and stronger and does not have any surge as low speed, low RPM. Am pretty sure the fuel pump replacement has helped. after driving about 40 miles, the SES came on again. Stopped at my local Autozone again and they ran the codes. Same codes for lean condition on both banks. I have a new MAF sensor on order and will replace that this Monday or Tuesday.

The car is still running very good and the engine is quiet, so I'm at a loss. I will be going back to indy shop Monday to have them run the codes, but I am hoping someone here might have an idea too. Doesn't matter if it's the dealer or your good indy, give them a problem without a clear solution and you might as well hook a vacuum to your bank account while they explore and fix every possible cause.

Again, thanks kindly to anyone who might have an idea on this.


09-17-2012, 06:20 AM
did you have a dealer or indy replace your valve cover gaskets or no???

if you did maybe they overtighten the bolts and now you have micro cracks in the valve cover it self..btw it was on e39 but all engines have same principle

i had around 14 codes causing my cel to come on...lean conditions..fuel cut off....multiple misfires etc etc....

went to replace my valve cover gasket and after cleaning valve cover from oil residue i have found multiple cracks especially around spark plug holes....since valve cover is made from plastic it can be from old age too...temperature...etc

used some jb weld instead of paying 200 bux for new one and more codes

on pics its hard too see but there were couple hairline cracks....also i had big vacuum leak at cvv at pressure regulating valve and vent hose....lean/rich conditions can only be vacuum leak or fuel as you know...

hopefully you will find the cause of cel...good luck

but funny thing is you had the system checked for leaks also cvv replaced...maybe its just MAF sensor like you suspected

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09-17-2012, 08:26 AM
Thanks very much for your reply and the pictures. Going back to my Indy today for further diagnosis. Hopefully, the MAF comes in today, too.

09-17-2012, 10:36 AM
let us know if the MAF fixed the issue....

10-04-2012, 05:08 PM
let us know if the MAF fixed the issue....

Installed the MAF and the engine defintely ran better, but after clearing the codes, they reappeared within 20 miles of driving.

Back to the shop. They kept it for a week during which time they did a large amount of research on the problem and were led to the Sbsr8 Sensor which controls fuel issues and air bag stuff. Apparently a very obscure and little known issue. They pulled a board off of another 745 they had long term in the shop and drove it around over the course of several days, putting about 50 miles on it. No further codes. They ordered one from BMW and installed it. Put another 40 miles on it to make sure no codes reappeared. Picked it up Monday and have put about 200 miles on it and everything is good.

Part was $389.72 from BMW. My shop didn't charge any additional labor since it was still a carryover from the original repair. Total with tax and environmental fee was $434.14. Combined with the new fuel pump and filter, total was $1470. Original dealer diagnosis was for all new gaskets and seals at $3,800...which of course would have left the problem intact.

Thank God for second opinions.

Part # is 65 77 6 970 892

10-04-2012, 05:48 PM
good to hear that you got the 7 running ....:thumbup: