I have a '91 740 non-turbo sedan with 70K miles. The battery is two years old and the alternator seems to be fine (the head lights stay constant when the motor is rev'd).

Recently the idle, when waiting at a traffic light, has -occasionally- started to fall to about 500RPM. It doesn't matter if the car is warm or cold but seems to be a bit more persistent when the head lights and other electronic components are being used. When the idle gets so low there is a major hesitation when starting to accelerate so I'd like to find a solution.

Thanks in advance, Ron