I have an 87 528e with 181k miles. Here are some of my problems (most critical listed first):
1. Starting recently, some of the instrument panel lights (anti-lock, brake, and battery) will flicker in unison when the car is idling. If I rev the engine above about 2000 RPM, they will go out completely, but when I return below about 1000 RPM, they flicker on again. (Maybe alternator or battery?) I tested the battery with a voltmeter. With engine running, reads about 13.5V. However, with engine not running, reads about 10-11V. It got to where eventually, the car would not start unless jumped. So, I put a new battery in. Same problems, but not as bad (the car starts now).
2. Sometimes when I push the accelerator to get the engine up to about 2500 RPM, the engine then falls back to about 1800 RPM (while the car is just sitting in neutral). When I let off the accelerator, the engine drops below 1000 RPM, but then recovers to about 1500 RPM. (Maybe TPS-related, car still trying to control idle when throttle is open? Or, related to same problem in #1 above?)
3. Whenever I shut the glove box with the engine running, the idle surges slightly up to 2000 RPM and then comes back down to 1500. Tapping on the Motronic ECU or the ICU above it has the same effect. Also, been having history of acceleration hesitation. (Maybe ECU or ICU?) Took out ECU and ICU and visually checked the boards and connections. Everything looked good, so I put everything back in place. However, still having same problems, not worse or better.
4. Whenever I step on the brakes a popping noise can be heard from the stereo speakers (all factory original equipment) whether the radio is on or not. Also, a consistent buzzing noise comes from the speakers all of the time when the engine is running.
Hopefully, I can find some answers here on the board. Thanks in advance.