SlickDizzy

For as long as I've had this car, it has had a really nasty problem where the revs will jump 200-500 every time you let off the throttle - it has a scary "surging" effect while in gear, and it makes shifting really rough because the engine is always going slightly faster than the drivetrain.

I've been told that the intercooler/throttle body boot is a likely culprit - 034 makes a nice silicone one, but at $75 it ain't cheap. The car has upwards of 250k miles, so I'm sure the whole vacuum system could stand to be gone through, but I'd like to pinpoint the problem a little more before I start throwing money at it.

Any suggestions are much appreciated!

audi_marv

See Autohausaz.com for the $28 intercooler hose. Take hose off, flex and hold it up to the light to check for rips. Oil in the hose is normal. Check Air Temp Sensor at front of intercooler hose while u are there.

Try pulling the trouble codes also.

Possible Idle/Throttle Position sensor issue, or area needs to be cleaned w/throttle cleaner.

The 3-Way Valve Cover hose connector, and lower Crankcase Hose are good vacuum areas to check. Clean your ISV with throttle cleaner while you're in the area, and check its hose connections.

yota-toy

does it do this while engine is still cold?
Is this car 10v. if so remove air cleaner and push up on dish. It should be very easy to push and should "slap" shut. If it creeps closed spray bomb it with intake cleaner. imo it does sound like a vacuum leak or ISV acting up though.

1989Type44

If you need any parts for you car - contact me I am parting out my 1989 200TQ. I have a post with pictures and a complete description of the car on this forum. Thanks.
Dave A.