So my '92 Golf GL has started idling at about 2000rpm consistently. It started about a week ago intermittently and now its idling at that speed all the time.
I've checked all the vac lines, throttle switch, oil cap, dipstick and removed and sprayed/cleaned out the ISV. Still the same.
So I found out today if I squeeze the vac line to the ISV (shown below) the idle drops significantly (500-600rpm). Correct me if I'm wrong, but doesn't this indicated that the ISV is not closing properly, thus allowing too much air through and causing the idle to increase? Also, when the ISV is disconnected and the car started there is no change (if anything the rpm rises a bit)
Does anyone have any help they can offer?