audineil

I have a '90 90 2.3 Sport 10V.
I have the usual idling problems and I have:
1)Checked for vacuum leaks - I can't find any.
2)Cleaned the ISV.
3)Replaced heaps of hoses including fitting the updated crankcase breather pipe.
4)Tried the ISV connected/disconnected.
5)Tried blocking off hoses from things such as the brake booster, carbon cannister etc.

My question is:
Is the ISV supposed to pass fairly unrestricted air when off the car and unpowered?

I noticed that the idle drops slightly when the ISV is connected (engine running) then tends to drift up again to around 1200 RPM then cycles between 800 and 1400RPM (sometimes violently speeding up as if the throttle is floored, when it does this the sound of rushing air is coming from the ISV).

Is the ISV supposed to be pretty much shut off when unpowered and is this my problem do you think?

TIA
Neil

cuatrokoop

Your car is CIS, there is a rather large relay that controls the ISV (aptly called "control unit for idle stabilization"). In the 5ktq I got (CIS as well), it came with one loose, and one in the car. I swapped the loose one in...and the idle went from 800-1500 or so, and back down, then back up. It also idled more rough with the "bad" one in the car.

The relay is located in the aux relay panel under the dash. Its big. Has a VDO sticker on it, with the VW/Audi logos and part number. Dunno if yours is the same, but the TQ uses 443-907-393P. The first 3 digits may be different, and the suffix may be different as well. The other numbers should be the same.