ashunter

1990 GT, Just had this car on a 2500 mile drive after mucho maint. Ran and runs great at all speeds. Now at my destination having probs. In drive at idle, engine roughness; w/ AC on it will cut out. Cold starts are no prob. starts right up, warm starts it does not start right up, after cranking a couple of times it starts but with a little smoke. In drive, standing still I get a pulsation in RPM. I,m a rookie with these things. Any help appreciated.

Rob Edwards

Sorry, I'm confused- when you say drive, do you mean in gear? Your GT is a 5-speed, right? Mine will pulsate while coasting in 1st gear at low rpm.

John Speake

As cold starts are OK (When O2 sensor is ignored) then it sounds like an O2 rather than MAF/temp2 type issue.

To bypass O2 sensor -

Disconnect battery ground strap (under edge of tool tray in trunk)
Unlplug O2 sensor (a small round 3 pin connector on the floor of the car, just in front of the large fue/relay panel in the passenger footwell)
Reconnect battery ground.
Start car, get it up to normal temp and see if improved.

Let us know how you get on.

killav

Make sure the idle switch is "clicking" when you let off the throttle. You can check this with the car off. Roll on the throttle just a bit, maybe 1/8 of the total travel, and let back off. You should hear a click when the throttle closes. If this switch doesn't close when you let off the throttle, the idle will hunt up and down, or surge.