High idle

[Chuckie86]

I've searched around and can't seem to figure out what else to do I have a 99 N/T and have a high idle. Car idles at 1700 with ac off and 1300 with ac on, and idles about 300 rpm higher when the car is rolling and goes back down when stopped. I have replaced IAC, TPS, Fuel Pressure Regulator and checked for vacuum leaks and leaks around manifold. I recently rebuilt the head due to timing belt snap. The car ran fine for three days then started with high idle. I have checked the timing 3 or 4 times to reinsure it is still correct. Almost forgot to mention car sat for 5 years before I rebuilt head. There is a sensor on the left end of the intake manifold not sure what that one is and if it can cause idle problem haven't replaced it yet due to not knowing what it is.

 

[Chuckie86]

No ideas and what I can check next?

 

[Brax93]

The sensor at the end of the manifold is the Manifold absolute pressure (Map).... check Throttle body gasket,check o2 sensors, EGR Valve stuck open, exhaust leaks, and dirty throttle body.... hope that helps some and since you checked for vacuum leaks.. that would be my first guess.

 

[jpc5364]

Mine does the same thing and playing with the Biss screw seems to help...I know it's not a permanent or professional fix but it might help. Good luck and let me know what it is in hopes that I may do the same!

 

[islandertalon]

Since you already checked for vac leaks, I would check to see if the throttle plate is closing fully. It maybe dirty and carbon/sludge is holding it open or the cable maybe not adjusted properly holding it open a little.

Did you clean the IAC portion of the throttle body when you replaced it? Have you put a fresh tank of gas in the car since it has been sitting?

Having a the car idle a little higher while moving is normal.

Ignore jpc5364

 

[Chuckie86]

Thanks for the input when I get back home next week I planned on cleaning intake and throttle bod. I did clean the IAC port aswell as map sensor port also plan on doing egr delete when I get back. I have disconnected throttle cable to insure it wasn't holding throttle plate open. Definitely put fresh gas in tank as I had to because when car originally went down I drained the tank. Has a new intake gasket (both of them) one thing I did notice with the gasket kit I bought it didn't come with a new TB gasket. I have spayed ether around it tho and got no pick up in idle. I have new o2 sensors in it as well. Hoping cleaning that nasty old intake and TB will fix it

 

[Chuckie86]

Figured it out thanks to the help from the input I got here. Problem was 2 things egr was leaking and TB gasket was cracked. Lesson learned either doesn't a sways work when checking for leaks vacuum leaks.