I have replaced a bunch of things on my 1985 740 turbo over the last year or so. One of the parts I replaced was the idle air control valve/motor. It worked very well for about a year. One way I could tell it was working well is that by turning the air conditioning on and off, the RPM would move very smoothly from 750 to 900 and back again.

Anyhow, it has worked well for a good while, but ever since I replaced the engine wiring harness and then fixed the a/c (which was out of commission for about 6 months) it seems to be malfunctioning. Today I turned the a/c off and the engine died while sitting at a red light. Several times when turning the a/c on or off, the engine RPM did odd things. Sometimes the RPM would shoot up to 1500 and then come back down. Other times it acted normally. The a/c is working just fine by the way.

I removed the IAC and cleaned it. It looked clean to me. One thing I found odd is that the door would open or close completely by rocking the IAC back and forth. I am not sure if that is normal. Is it possible the door came loose from the motor ? I have not taken one apart to see how they work, but I find it a bit odd that it will easily flip all the way open or closed by rocking it in my hand.

So my question is, do you think my IAC has gone bad, or do I have some other problem perhaps with the new wiring harness. Maybe the pins are reversed.

Thanks for any info.

R Duke