Hello everybody . Say I got a problem which I have been trying to nail down for some time I have a 92 z28 5.7 TPI which some times it idles a little high . It seem it happen when I'm at a stop light and it just jumps up in idle. Now it doesn't always do it but it seem its doing it more sense the weather has gotten hotter well that's what it seems I could be wrong . If you guys have any ideas I would love to hear them.

 

I'd look for a vacuum leak. TPI can hide leaks in a lot of well hidden places so the carb cleaner trick sucks on these but a smoke machine makes it easy (a homemade one works just as well, so you could search that out). Could be the egr sticking slightly or the map sensor failing but I'd be more inclined to expect a vacuum leak. They're the easiest thing to be a problem so check that first.

 

Thanks for the reply. I've been looking to see if there's a vacuum leak with no luck so far but I've been wondering and I could be wrong but I was thinking that the brake booster maybe bad I know it runs off vacuum and the car had been setting up for some time, But I'm going to try again to see if I can find a vacuum leak.

 

Have you tried to deep clean the throttle body and IAC valve? That cured my idle problem. Just be sure to re-check the 4 TB bolts after a few drive cycles, mine loosened up and needed to be re-torqued. Also wouldn’t be a bad idea to try the TB coolant bypass to make cleaning much easier.

Another idea is check your TPS voltage, should be around .054 and with voltmeter attached run the throttle up and down to check for steady readings to go up and down.

 

His 92 is speed density, it doesn't care what the voltage starts at unlike maf, but the steady reading is important.

 

Ahh, I’m not familiar with the “newer” speed density, my bad.

 

Thanks for the info guy, I change the IAC out some time ago and the TPS as well as the map sensors and I even put on a new EGR . Some one in the past bypass the throttle body coolant line so its no longer hooked up and I did clean the throttle body but maybe I didn't clean it enough and that's a good point about the throttle body bolts I need to check that.

 

Did you ever fix your high idle issue?

 

Well kinda and I'm not sure if it was anything i did to fix it . When i crank the car up and let it warm up it seem to idle fine but what it dose is when driving down the road and when you are coming to a stop it seem to be idling just a little high but when you come to a complete stop the idle drops down to were it should be. If that makes any sence.