Questions about High idle

**Dakoda** · 03-04-2013

I have a 99 gtp only mods are a 3.5 pulley, plog, 3in downpipe. Now my problem is that it seems to have a little bit of a high idle. When i cold start it it idles at about 1500 for a min or so then drops down to about 1100. From what i have been told it should be down around 900 rpm's so im just looking for possible causes of a high idle. I have cleaned my maf, tb, replaced spark plugs and wires, fuel filter, and all new vacuum lines. Any help is appreciated

**Fivefingerdeathpunch** · 03-04-2013

Have you touched or replaced the IAC or the TPS yet?

Both of those do control idle speed and send signals to determine rpms and many other things.

**Dakoda** · 03-04-2013

I haven't messed with either of those... i know on my last car the tps was a pain in the a$$ to set so i didnt really wanna go into that again.

**Dakoda** · 03-04-2013

Is the iac just a quick swap or is it adjustable?

**ericspecullaas** · 03-04-2013

A vacuum leak can cause high idle as described.

**Dakoda** · 03-04-2013

i had a vac leak at the egr tube and egr gasket but both are fixed now... it idles a little smoother but still a little to high

**BillBoost37** · 03-05-2013

What does a scanner say? Does the scanner at full temp say that it's higher than the spec or that your tach aka cheap gauge is off?

**Dakoda** · 03-05-2013

I still need to get a scanner bill... i just dont have the money right now otherwise i would have one. And i dont know anyone near me that has one either im supposed to be going to meet greg badass sometime in the near future to deliver his seats and he said he could scan it for me when im there

**BillBoost37** · 03-05-2013

Ok, reason I ask is I've seen many guys say their idle is off...and it's the gauge. I've also had a guy with high idle (throws a code) come to me. His was simply the cables doing their loop over the strut. Adjusted them and poof.. fixed.

TPS can cause a high idle if it's not reading properly, need scanner or voltage test to check that.
IAC typically doesn't cause a high idle.

**Dakoda** · 03-05-2013

I cleaned the iac today no difference at all.. and im not going to mess with the tps until i KNOW for sure that its not just a faulty gauge..

**DoubleBlown** · 03-05-2013

i have the similiar problem as you when using the lq4 maf i get high idle at cold starts sets of the ses but if i use the stock maf on the tb it idles fine

**Dakoda** · 03-05-2013

Mine is all stock.. and it idles smooth the guage just reads right around 1100 to 1200 rpms once its warmed up...

**ericspecullaas** · 03-05-2013

Originally Posted by Dakoda

Mine is all stock.. and it idles smooth the guage just reads right around 1100 to 1200 rpms once its warmed up...

the higher your car idles the more gas it burns and the hotter the cylinders get meaning preignition. Also too they may not apply but the RPM gauge could be off by x% i have a 92 camaro that reads 1500 rmps when its at cold idle and i have been to lazy to fix it. Never assume that your idle is fine when its over 1000 rpms. Also if it back fires through the SC or the NA intake it can cause a broken time gear tooth. Do that to many times and your computer will be frying the engine. so yeah no high idle lol. I know BillBoost is correct because it is electrical and they do fail from time to time. Personally before i say its the gauge i spray with carb cleaner to make sure i have no vacuum leaks then check the voltage to make sure im with in range.