Is my ICV bad?

[thefork]

1990 325i

Problem: The car seems to idle a little rough...a slight 'rumble' every few seconds can be felt, and a very slight fluctuation in RPM at idle. When I turn on the AC the RPM jumps up to 2000.

Could this be an ICV problem? The ICV has a buzz and vibrates with ignition at ON position. I removed the ICV, cleaned it up a bit with throttle body cleaner, and checked for continuity. All within spec. However, when I unplug the ICV with the car running there is no change in RPMs. Is this a sign the ICV is bad?

[thedeal]

no

[jlevie]

No change in idle when you unplug the ICV could be a bad idle switch in the TPS.

[thefork]

I tested the TPS for continuity and voltage as specified in the Bentley manual. All was within spec. Can I rule out a faulty TPS?

[jlevie]

If the idle and WOT switches in the TPS show zero ohms when activated and if the idle switch is closes with the throttle arms is just off (0.030-0.060") the stop screw, the TPS isn't the problem. Since the ICV buzzes when the ignition is on, it should be working. That combination suggests intake leaks as being the cause of the poor idle.