In Reply to: Rough idle....Hell, WHAT IDLE (help!) posted by Chandler Ogden on June 14, 1999 at 16:20:29:
: I fear I have a gremlin to track down....Car ('85 535i) ran great into work today. First rainy day in a long while in these parts. Went out at lunch, and as soon as I pulled out in traffic, the car ran extremely poorly and would not idle at all. At 2K+ rpm, it seemed to do OK, but still ran rough and missed (just not as obviously). I brought out the collective "brain trust" of auto knowledge at lunch after limping back to the office, and we were stumped. I have new plug wires (2 months), plugs (4 months), cap and rotor (6 months). Seemed to be obviously missing on at least one and probably more cylinders.
: Now the poser. After fretting all afternoon, I left early to limp home, and the car ran PERFECTLY for 9+ miles. (Now sunny and hot). In the last 2 miles, same bad missing problem as earlier.
: As I delve into troubleshooting, any theorys out there? I am leaning towards an intermittent electrical problem, possibly one of the fuel pumps.
: All thoughts appreciated!
I bought an '87 535i about two months ago that is now exhibiting the same symptoms. I drove the car into the garage one night (running perfectly) and backed it out the next morning, unable to keep the car running. The engine would completely cut-out at all RPMs below 3-4K. I drove the car (barely) to my local BMW mechanic who quickly identified the problem. The electrical connector which attaches to the mass flow control box (the square metal box between the air cleaner and the inlet for the fuel injection) had come loose.
Although I have experienced this problem since then, the problem stops by moving the connector/cable assembly around. I'm not sure, but I suspect that the butterfly valve which monitors the air intake may need attention too.