chevelless502

Ok, going to try this again as i cant figure it out for the life of me. I have 1998 Z28 A4 and it has a high idle issue that will not stop. What it has been doing is you start it and after a very short time it will begin to idle up almost instantly and it will go to close to 3000 rpms. The only way i can get it to come back down is either shut it off and let it sit for a long time or a couple times i have unhooked the battery and it will go back down but only for a short time then be right back up again. Well i did more research online and lots of people said it sounds like a vacuum leak. Tonight i did yet more checking of vacuum lines and such. All i could find was one that looked "maybe suspicious" that went to the throttle body. I put a hose clamp on it and started the car. The idle was PERFECT and it sounded really good. I let it sit idleing in the driveway for a bout ten minutes and then shut it off. Went back to it about 5 minutes later and started it and it was perfect again. I thought well maybe i got it. I decided to take it for a drive and drove about ten miles went thru a drive thru for supper and shut it off to eat. Started it back up after about 15 minutes and with in about 10 seconds...BAM....right back up to around 3000 rpm and it stayed there all the way home. When all of this tarted is when i changed out the throttle body for a different one. I have since put my old one back on as well as tried several TPS units as well that i have. Any ideas or suggestions is greatly appreciated.
Thanks

Mike_hawk

I agree that it's probably a vacuum leak, if you think it's a hose pull it off while the car is running and cover up whatever port it's coming from on the intake with your finger. U could change the intake/throttle body gaskets to eliminate those since they are pretty cheap. Since you mention that you changed throttle bodies have you looked at your throttle body when it idles high to make sure the butterfly is closed and not hanging or gunked up?

nascarnate326

iTrader: (1)

unplug TPS sensor, and IAC sensor...key on(don't start) wait a few seconds. Key off...key on(don't start) wait a few seconds. Plug in TPS and IAC and then start it up. See if that makes any difference.

chevelless502

WE HAVE A WINNER!!!!!! Thanks a ton!!!! That did it. Man was that frustrating.

Thanks again,
Andy