I posted a question about a high idling problem last weekend after my trip to Vermont. Thanks for the answers, they were all pretty good.
I purchased a brand new Idle Air Control motor from Ebay a few years back and changed it out last spring just to be on the safe side. Even though it was working perfectly, I thought that the old one in the car was destined for failure because it had over 300K on it.
I spent the good part of my Saturday morning this weekend replacing that new idle air control motor with the old one. Because I had a problem with the new one sticking over the summer, causing a fluctuating idle, I had myself convinced that it was stuck, permanently this time, and had to be the problem causing the high idle speed, even though the high speed was steady, and the fluctuating idle problem was cured with a tiny squirt of WD40.

WRONG!

I spent the rest of my Saturday hunting down a throttle body to intake gasket so I could clean the throttle body and possibly replace the throttle position switch. I have a good one laying around from a car I parted out. My search was unsuccessful, and I ended up buying gasket material and a pair of scissors to make my own.

This morning I was ready to pull the throttle body. I looked at the throttle cable and remembered this, the very first response to my query last week: "Check the throttle spool and make sure that the cable is releasing fully when you let off the gas pedal. It may be holding the throttle slightly open." I looked at the cable, and it was a little loose on the spool. The gas pedal was releasing fully, but there was still a little slack in the cable. Even though the Brickboard answer wasn't perfectly accurate, it got me thinking. Then I checked the obvious. There is a throttle stop screw on the throttle body to make small adjustments to the position of the cable spool plate. The screw is held in place by a locknut. I never touched this adjustment, because the car always idled perfectly and the locknut was always tight. In my rush to judgment about this problem, I assumed the screw and locknut were tight. Guess what? They weren't. I cannot figure out how they got that way, but my guess is that while driving on the turnpike for hours and hours at high speed, vibration loosened the nut and the screw turned clockwise(why not counterclockwise? I dont' know). This tightening of the screw held the throttle cable plate position out farther, opening the throttle body more thus creating the small amount of slack in the cable, and the high idle when I stopped for fuel. A few turns of that screw, and a tightening of the locknut were all it took to get my brick idling quietly and smoothly again.
My point is, I guess, that you should always check the most obvious things first and rule them out before going nuts with the more complicated solutions. I hope this helps someone out there in Brickland.




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