High Idle after engine warm

What would cause the engine to idle high after it is warmed up?

extankerguy said:

What would cause the engine to idle high after it is warmed up?

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Assuming you have verified it isn't the TPS, IAC or a vacuum leak whether in the manifold or elsewhere like a hose, I had this same problem that eluded me for two years! It usually was more pronounced after shooting the throttle body plate with a can of intake cleaner, and only after warming up.

So... try inspecting the throttle plate itself for misalignment in the throttle opening. Mine was misaligned, just barely, but enough to cause it to stick just enough usually causing a 1,100 - 1,300, and sometimes higher, idle. I loosened the two screws just enough to reset the plate so it was perfectly centered in the bore when in the fully closed position.

What I suspect was happening was as the throttle body expanded due to the heat radiating through the intake manifold, the misalignment allowed more air to pass, even with the IAC fully extended. Also, with the built up carbon cleaned away, there was nothing impeding the flow paste the misaligned plate. Since you have the same three bolt throttle body as I do, it's a possibility. If this works, please post it so others can read.

Check the intake manifold bolts and make sure they are properly torqued. They seem to come loose and cause a vacuum leak. My truck did this for years before I found out what it was.

Katarn

Tightened manifold bolts yesterday. Now the idle is finally normal!


Thanks again!

Happy to help.
Katarn