setting idle speed?


Founding Member
Jan 29, 2001
Whats the proper way to set the idle of my 90gt, I keep getting code 66 and a check engine light comes on and goes off every so often, I did some research and found out that the throttle plate being too high may be my problem, so whats the proper way to set the idle?
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look on top of your throttle body and adjust your TPS sensor for starters. if you are unsure how to do that, you can find it on the internet.

pretty much cut the shielding off the green and black wires and use your multimeter and check for volts. you want it to sit as close as possible to the .96-.99 range. to adjust it, take a screwdriver and loosen/tighten the screws until it sits in that range. you shouldnt have to tighten/loosen it by much (if any at all).

once that is done, you can use an allen wrench and adjust your throttle plate to where you need it. if i remember right, the base idle for a 5.0 engine according to my chiltons manual is 700 rpms.
The tps should be in the .85V-.95V range; any closer to 1V at idle can cause idle/mixture issues. The computer controls the idle speed on our 5.0L's. It uses the IAB solenoid and timing advance/retard to maintain the idle speed around 675 rpm. That's built into the ecu. If you're trying to get it back to stock operating conditions, pull the throttle body and iab solenoid and be sure they are clean and operating properly. Back the throttle stop screw completely out, insert a .003" feeler blade between the stop screw and the linkage, and tighten the stop until it just touches the feeler gauge. Turn another 1/4 turn past there - that's where the throttle plate is supposed to sit. With engine warm, key on, engine off, measure tps voltage as decribed in the previous post. If it's in the .85V-.95V range, leave it alone. It wasn't designed to be adjusted and chances are if you get the throttle plate back where it should be, the tps reading will be correct. Disconnect the battery for a bit to clear out the error codes. Restart and drive the car a bit so it can 'learn' about the changes you've made. See what you've got then.