530i (E39) Rough Idle/Stalling

[pfaber]

Folks, I need some diagnostic help, and so does the car.

I've a 2002 530i that idles poorly and stalls at traffic lights. Actually, I've not experienced the stall but my wife has several times. I will attest to the rough idle. I used my Peake scanner and I get two major codes:
1. O2 Adaptation Limit
2. O2 Sensor Control Limit
There are a series of misfire codes for all cylinders but I thing these are the result or symptomatic of the above two.

Also, there is a sharp metallic or clacking sound underneath the intake manifold that is periodic. Sounds like a very loud soleniod action or perhaps a backfire.

The car has 120K on it so I've recently replaced all four O2 sensors and the plugs. Recently I found the rubber vacuum line to the Secondary Air Diverter Valve cracked so I replaced it and traced it back and replaced at the opposite end as it was also deteriorating.

I've also put a new throttle body on the car for another issue.

I really need some help with this. Thanks I appreciate it and so will my wife as she is now driving the old cherokee and wants the 5'r back.

[marti5]

Did you clear the codes after you replaced the o2 sensors ?....If you did and these are new then I would say you have a vaccum leak or the MAF is playing up...unplug the MAF and see what happens..

[pfaber]

Sure did, and after I repaired the broken vacuum connection. Codes came right back. Thanks

[marti5]

Try unplugging the MAF....

[pfaber]

I should have suspected that. I unplugged the MAF, the engine quit andI restarted. Smooth idle and no solenoid on steroids sound.

I recently replaced the MAF on my VW TDI. Those give you a pretty good sense of their failure. They start to slow down until the performance of the TDI rivals that of an old diesel rabbit; my old vw bus was faster (for a frame of reference). Unplug the MAF and it goes like a real car ought to.

I just wonder why there is no MAF code on the BMW or the VW. It must be a German thing.

Thanks, no off to BAP/GEON for that sensor.

[marti5]

Peake code reader dont seem to but carsoft V6.5 does, anyway glad you know what it is now, have a nice weekend.

[bwatters]

I have exactly the same symptoms on my 2001 with 140K, including the solenoid on steroids noise. Did replacing the MAF solve the problem? That's a $400 part! Is the a way to test it to confirm it has failed?

[bwatters]

Rough idle update. When working my way into the ICV for cleaning I noticed my intake manifold runner valve was damaged. It was not longer connected at the actuator end of the flapper. I replaced the part last night and when I started it up, it purred like a kitten. Problem solved. Thanks for the DIY stuff that lead me to clean the ICV and ultimately to the root cause of the idle problem. I wouldn't have gotten to it without BimmerWerkz to guide me.