2004 Very High Idle

[dadooishome]

Okay, I found out *all* the extra air for the high idle is coming through the idle bypass circuit. The brand new idle control valve is doing something extremely sinister- it randomly decides what speed the idle should be, and it does this even when the 4 pin plug is disconnected!!! Grrrr.

So each time I disconnected a component (EGR, TPS, PCV) it would go to a normal idle for a few minutes, hours, even days.... then go back to a completely random high idle. (though it is a bit temperature related)


Therefore I plugged the idle hole in front of the throttle butterfly valve- thus taking the entire idle circuit completely out of the equation. Now it never idles above 800 rpm. So I can now drive the car, but not very well when it is still cold.

I took my analog meter to check the 4 wire inputs to the idle control valve. There were three things which are very strange:
1) none of the 4 wires is a ground
2) with the engine off, each of the 4 wires measure about 20k ohms
3) when the engine is warm, all 4 of the wires would "pulse" between 1v and 11v at a one second interval

So is this the normal input for the 4 wires? HELP!

[xintersecty]

After doing some more reading, the valve could be dirty or just bad. With the engine cold you should be able to remove it, leave it hooked up, plug the hole to the throttle body, the valve should open up all the way.

Then again, the valve should close when hot keep the idle close after your engine warms up the valve should close. to get it back to a decent idle.

[dadooishome]

Finally resolved this issue by buying a used throttle body (which included the TPS and IAC) for $45.
Car-Part.com--Used Auto Parts Market

Found out both of the new IACs I installed were bad and had failed in the same manner as the original IAC.
What are the odds of that happening?
So I chased this problem for 6 months.... when the first component I replaced should have fixed it.

Lesson learned: the $12.50 Amazon/Made in China IAC was not much of a bargain.
Thanks for all the help.