It has a variety of causes, most commonly a badly adjusted carburretor, or problems with the injectors. No way to tell cost of repair.
Vacuum leek
the choke is on
did you find a solution yet
The cause of high engine idle and surges in the 1989 Corvette is due to..Read More
a/c kicks on
Electronic Fuel Injection System. Go to a repair center.
Either your fuel is burning too rich or you have an idle censor out. new idle censor's are not expensive
Could be several reasons but a vacuum leak would be most likely.
A sticking choke or vacuum leak are two common causes.
Could be a vacuum leak
Check throttle positioning sensor.
There is not a low idle screw. The computer sends a signal to the idle air control motor and it does the adjusting accordingly. If your idle is to high and your check engine light is on then you need to go to a repair shop and have them diagnosis the problem.