How freely should an ICV turn?

[Gavin]

I’ve had a very minor bouncing idle for as long as I’ve owned my E30. But in the cold of my BMW’s first winter the car idles like ass, and yesterday it threw me a CEL. Since the intake rubber looks original I have always assumed my idle issues were caused by vacuum leaks and a bad/sticking ICV.

I pulled my ICV valve out today and noticed while cleaning it that it turns completely freely, there is no resistance to turning at all, should there be? I’m pleased the unit was not seized up, but I thought there would be some very minor resistance to turning the electric motor?? It almost seems as though it’s broken and just sort of flopping around.

[PeaveyBassist]

It should move around a lot. If you take it out and hold the motor part with the valve at the top and twist it fast back and forth with your wrist the little ball on the inside should bounce back and forth a lot.

Will

[jlevie]

It should turn freely.

Does the idle change if you unplug the ICV? It should.

Can you feel the ICV buzzing?

An erratic idle can be caused by an intake leak, bad or sticky ICV, misadjusted idle stop or TPS, bad AFM, or bad O2 sensor. Given the age of the car the first thing I'd look for would be an intake leak. Then I'd make sure that the idle stop and TPS was correct (procedure is in the Bentley). With all of that correct I'd check the signal to the ICV and whether the idle changes when it is unplugged, replacing the ICV if it isn't working. If original I'd replace the O2 sensor and I'd verify proper operation of the temp sensor that feeds the DME. As a last resort I'd swap out the AFM to a known good unit.

[Gavin]

Excellent, sounds like I’ve got a plan. I appreciate the help.