My car is a 1993 Buick Le Sabre with 75,000 miles on it with a 3.8 engine in very good condition except for one problem.About half the time I take my foot off of the accelerator, the engine has a very high idle.Thinking that it might be a vacume leak,I checked all of the vacume hoses for leaks, but they are all good. I replaced the IAC idle solenoid, but that didn't make a difference either. Sometimes the car will idle fine, but some times it can idle at up to around 2,500 RPM's. Any help would be appreciated. Thank You, Bill Eagle

 

get a tech 1 obd and make sure the tps sensor signal is between .33 volts and .47 volts. if the tps is out of adjustment it will fool the pcm to make a default signal. the tps is the most important sensor for timing the correct spark to fuel delivery. id check that first.