Mechanics

WHY IS MY IDLE RUNNING HIGH?

1990 Chevrolet Lumina • 68,000 miles

What would make the car idle too high on start up but slow down as soon as you started driving it? I recently did a bunch of work to the car replacing the fuel injectors, crank position, throttle position, coolant temperature and oxygen sensors and the thermostat. I also replaced the intake manifold, plenum, throttle body, EGR and valve cover gaskets. Changed the spark plugs and wires. The car has been running great and now all of a sudden it idles too high on start up with a cold or warm engine. Today I let it run for a minute and the check engine light came on. I turned the car off and checked under the hood to make sure all the wires and connections were tight and they were. When I turned the car back on there was no light and it never came on again. Any ideas?
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Tinkergirl
December 15, 2011.



First, have the computer scanned to identify a trouble code. It will tell you where a problem is coming from. Also, most parts stores will do it for free.

Next, check for vacuum leaks and make sure the idle air control solenoid is working properly. Either one could cause an idle problem.