Just started out of the blue. Idles approximately 1500 rpms when at operating temperature. Also surges when cruising at lower speeds but not under acceleration or WOT. Does this sound like the IAC on the throttlebody might be carboned up? Thoughts appreciated. Thanks.

 

Follow-up.....cleaned the IAC and all is back to normal!

 

Where exactly is the IAC on the throttle body and how did you clean it?

 

The IAC is the "Idle Air Controller" and operates a pintle type mechanism regulating the air intake at idle. With the "butterfly" in the throttlebody being closed at idle the pintleallows a small amount of air through the pintle seat to allow the engine to idle at a pre-determined RPM. Carbon can build up and hold it fromits normal position and a high idle is usually the result. It is located on the side of the throttlebody and two bolts attach it to it. Electrical connection must be unplugged and inspected also.

 

Thanks for the reply. This gives me something to check. It makes sense that the butterfly would be held open resulting in high idle if the IAC was not operating right. The problem I have is when I look at the engine there are so many gadgets under there I need an idea where to look. Also on this forum I got a lead that it could be a loose wire to the temp sensor. Again thanks much.

 

A vacuum leak is a good source of a high idle also. Check all vacuum hoses for splits and fitment.