Hello, I have a 1986 740 wagon. Whenever I go out to start the car in the morning, it never idles up after start. It starts just fine, but it stays at a steady 500 RPM idle. Is there a cold start sensor of some sort that could cause this. Runs great and RPMs creep up within about 7 min, I would just like to solve this. Starts and idles around 800 RPM after up to operating temp. Any help appreciated. Thanks

 

Your engine has an idle motor. It's purpose is to raise the idle above normal speed when started cold (by allowing more air into the intake manifold) and to keep the idle steady when a load such as the ac compressor, alternator or steering causes the idle to go below normal speed. The armature in the "motor" does not spin, it wiggles back and forth and eventually the brushes will get stuck (or fail to make electrical contact) in grooves that are worn into the commutator. First test is to listen to the motor with the engine running - it makes a constant buzzing noise. Sample idle motor below

 

Thanks for response. I forgot to mention that I did clean the IAC valve about a month ago and it sort of made it worse. Any ideas? I might think about replacing it now.

 

Before purchasing something you MIGHT need - How about testing it?

Remove the idle motor (leave it attached electrically) , plug the two hoses and start the engine. (if it still idles, if not you will need to open the throttle plate slightly) You will be able to watch the idle motor open and close as needed. For instance - unplug one injector to slow the engine down and watch the motor open up to allow more air -