Dies at the light

Hey folks! I have a 1990 BMW 525i with 298,000 miles on it, and it’s still going! Kind of. When I come to a stop, the engine will kind of rev once or twice, or maybe not at all, and then die. I then have to restart the car and keep the rpms up enough so it won’t die at every light! I have replaced my oxygen sensor, spark plugs, distrubutor cap and rotor. I am reluctant to pay the $250 bucks (yes!) for new spark plug wires if this probably won’t work either. Any take on what the problem might be, or do I just have to keep going, next replacing the air filter, fuel filter, etc? PS, anybody want to buy a red 1990 Beemer?

You’re describing what happens when the Idle Air Control/Air Bypass motor no longer functions properly.

This component is what controls the idle speed anytime the accelerator is released. You might try removing the motor and try cleaning it and idle air bleed port on the throttle body to see if this helps. If it doesn’t, suspect the motor itself.


Thanks, now where is the idle air bleed port on the throttle body, and what’s the best way to clean it and the Idle Air Control/Air Bypass motor?

It could also be a vacuum leak. My experience is when this happens consistantly at stops, check the power booster for the brakes for any leaks or odd behavior. The power booster uses engine vacuum, and a leak will behave like a bad vacuum leak, as your describing. The engine revving before dying was my clue. Many cars will rev up and down when a vacuum leak appears.

BTW, I had 325,000 miles on my truck, and running like a top until a retaining wall had other ideas. I wouldn’t give up on this ride yet.