Idle keeps going up to 1200rpm

[lordGeo'SX]

Hey guys,

I have a 99 had and I've been ha ing issues with the idle. For some reason my idle keeps climbing back to about 1200rpm after driving it. I already replaced the IAC and the throttle body, replace the gaskets I adjust the biss screw to set the rpm around 800rpm, but as soon as I drive it it goes back to 1200-1500. Sometimes when I turn the AC it drops to the point that the car dies, and other times it regulates it self to 500rmp. I just order a new biss screw kit, since maybe the boring on the one is bad. Any ideas will be welcome.

 

[92AWDHX40]

Check for boost leaks for starters.

 

[lordGeo'SX]

Check for boost leaks for starters.

A mechanic check it for leaks and found one in a hose going to the turbo and got fixed. According to him, there are no other leaks.

 

[chrysler kid]

A mechanic check it for leaks and found one in a hose going to the turbo and got fixed. According to him, there are no other leaks.

No sir. Not a valid answer. Pre turbo is a vacuum leak.

It sounds like a cruel answer, but it's time to put on your mechanic hat and realize your basic mechanic will not be able to fix your car.

A boost leak test involves removing the turbo intake hose and using a coupler to pressurize the turbo charger using a bicycle tire pump or pressurized air.

If you are taking it to a mechanic you need to specify you want a boost leak test and want to know the amount of pressure leak down during testing. "No leaks" is not a valid answer. Your mechanic would tell you "at 15psi I pressurized the system and sprayed soapy water around the post turbo pressure system and observed no bubbles and the car held 15psi."

 

[lordGeo'SX]

Oh wow... very insightful response, thank you Chrysler kid, I'll make sure to do that. Just an update, in the past 24 i was able to set the rpm to more or less 800 without any fluctuations after driving sessions. The current issue now, is that when I turn the A.C. on the rpm drops to zero and the car dies. Woul it be safe to infer that is related to a possible vacuum leak?

 

[93AWDDSM]

What's your vacuum at idle on your Boost gauge?