I have a 1993 945T. I took a look at the idle control valve today and have some questions. The valve was somewhat stuck, but after cleaning with throttle body cleaner it moves fairly well. Something that was odd is that when the valve is closed (aganist the stop), it appears to be closed too far such that air can pass though it. Rotating the valve about 1/8th of an inch prevents air from flowing through the value. Moving it further opens the valve, as it should. It looks like the stop was adustable and set at the factory. Now it has a locking epoxy (?) preventing adjustment. Should the stop be adjusted so that the valve is actually closed or is there some other reason that it should permit the passage of air when on the stop?

My car has somewhat of an unsteady idle, which is why I took a look at the valve. I also just cleaned and adjusted the throttle body.

Could someone explain the signal that the idle control valve gets? Is it just 12V or 0V, or does the signal range from 0-12 volts (eg 0, 1, 2, 3, 4, 5, 6, 7...12V)? Is the valve either open completely or closed completely, or is it variable?

Finally, what lubricants (if any) should I use on the valve?

Thank you,
Steve
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1986 745 w/ M46 200K since new, 1995 965 104K

Hi
I have 91, 940SE and I have the issue that the engine vibrates/shakes when idling. I had cleaned IAC a while back. I opened it again and its is fairly clean. As you mentioned I noticed that the valve is not closing all the way. I would also like to know if this is designed so or it is supposed to be closed all the way. I am desperate to find the reason for vibration as the vacuum and other lines are checked already. May be someone can lead us out of this.
Thanks

Someone else noticed that the valve is open when against the stop, so it must be designed to be like that. I don't know about your rough idle, but one possibility is the intake manifold gasket. Others with more experience can probably suggest other things.

Best,
Steve
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1986 745 w/ M46 200K since new, 1995 965 104K

Dear Steve,

Good p.m. and may this find you well. I have handy a Bosch Idle Air Control Valve and a Bendix (VDO) Idle Air Control Valve. Each is in good working order.

The Bosch valve - which rotates - "at rest" is open about 3/32" (3 mm).

The Bendix valve - which reciprocates - "at rest" is closed.

So far as I can see - or have read - these valves are not manually adjustable. Rather, their operation is governed by the ignition/engine computers.

The valves are operated by electric motors. If the valves are dirt/carbon-free, motor wear can produce rough idle. When the motor fails, the valve must be replaced.

Hope this helps.

Yours faithfully,

spook

Hey Steve,

I was actually doing the same maintenance on my 940 this weekend. I can tell you that I noticed the same positioning of the IAC valve, it seems to be slightly open. My feeling is that its unlikely that the set screw has worn out of place (the epoxy was intact, I doubt the screw tip could be ground down by the valve opening/closing) and some small voltage is sent to the valve so that it closes fully when in operation. Sorry I dont have a better answer, just my guess

Mike

Hey Mike,

I think that you are right - the stop couldn't have worn down that much. Glad to hear that it closes when in operation.

After cleaning your's did you lube it up with something?

Thanks,
Steve
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1986 745 w/ M46 200K since new, 1995 965 104K

Does anyone have a photo of a working idle control valve, looking into the valve from the side port (ie the port closer to the intake)? I want to see if the "closed" position of my valve is correct.

Thanks,
Steve
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1986 745 w/ M46 200K since new, 1995 965 104K