idle problem
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Joined: Feb 2005
Posts: 79
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idle problem
on my '78 vette i had the idle set to 600 low 1600 high, which made it curb idle at 500rpm. now all of a sudden it idles low at 900 still at around 1600 high, and the curb is at about 600. i would adjust the idle speeds again myself this time to know it was done right but on occasion when i first start the car after its been warmed up it idles perfectly. and only after a few miles of driving does it start to idle high again... Also there seems to be a really small backfire every now and again, just a little bump only while im at curb idle with no audible 'pop' i have no idea what could be wrong... 
Instructor
Joined: Sep 2004
Posts: 193
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When it starts idling too fast, carefully pull off the air cleaner with the engine running and look between the choke and the carb to see if the fast idle cam is straight up and down or maybe even at 45 degrees. I can't imagine what might cause it to re-engage; however, with cars as old as these, I suppose anything is possible.
The other thought is about a/c - if you have a/c and set the idle speed with the a/c off when it engages it will also boost the idle speed to keep the engine going. There is a plunger in front of the throtle linkage that engages and pushes the linkage to a higher speed. You can adjust that plunger to change the speed.
The other thought is about a/c - if you have a/c and set the idle speed with the a/c off when it engages it will also boost the idle speed to keep the engine going. There is a plunger in front of the throtle linkage that engages and pushes the linkage to a higher speed. You can adjust that plunger to change the speed.
