chevelless502

I have a 98 Z28 A4. It has recently started to rev up wildly on it own at random times. Sometimes i will start it up and it will idel fine and i will drive it a few miles then it will act like the throttle is stuck on it and want to idle up at 2000+ RPM. Other times i have started it and it will instantly idle up to 2000+ rpm. I have got out at that time and tried to manualy pull the throttle back and it is already fully back. Any ideas?

Thanks

777Shock777

iTrader: (5)

This may not be the problem, but when mine started doing that it was actually the throttle cable.. - The tabs on the Throttle body that hold it were broken so it wasn't tightened and would occasionally get stuck on its own.

chevelless502

Any other ideas?

PhoneniX

if the increase in RPM is only at idle I would first look at your MAF. The easiest way to check it out that i've done is by switching mine with a friends for a test. A dirty or failing MAF could cause the ECM to increase fuel raising the RPM at idol yet not be as big a problem as say a stuck cable while driving.

patSS/00

iTrader: (6)

Definitely check the IAC valve. They get plugged up with carbon and stick open. They're pretty cheap, and easy to replace.

LS6427

iTrader: (2)

Increasing fuel ALONE will stall the engine if air is not increased along with it. Also spark needs to be increased to, or it will stumble and stall.

I agree about the MAF......easy to swap it with another one. But what a bad MAF does is make the IAC valve open and close....causing the increase in rpms.

Air going into an engine...EXTRA air from another source......is the only way an engine can rev up without the throttle blade being open.

.

dtws6

you could check the pcv hose for a crack or another vacuum leak.

WS.SIX

iTrader: (3)

Make sure your egr tube is tightened down and not leaking. Or if you deleted it make sure the delete plate is not leaking.

Streetlegal?

iTrader: (25)

I'm going to try this when I get my car out of storage. Once I had my car tuned for my ls6 intake, long tubes and exhaust my my car started randomly kicking the idle up to 2000ish RPMs when I would come to a stop. It wouldn't do it all the time and it would hang there for a bit then come back down.