macdaddy1989

i have and 89 gt that when cold has check engine light on and idles fine, but when warm check engine light goes off and idles at 2000rpm. i have already changed all vacc lines, new egr valve, egr position sensor, Throttle position sensor and IAC. also cleaned MAF 2 times with MAF cleaner. I have been told it could be the MAF, o2 sensors or the IAT( Intake Air Temp Sensor (AKA Air charge sensor)). Does anyone have any ideas??????

mattdel

If the MAF was bad beyond cleaning, it could cause it, but generally it wouldn't run right at any RPM either, so that's your call. o2's wont cause it, neither will IAT. The ECT will though(engine coolant temp), which is located to the left of the distributor near the #1 injector. This sensor would have to be giving really really wacked readings to do this, though. Check the tech articles for a sticky I wrote about running rich. The same test would apply to check to see if this sensor is the cause of the high idle. You'll be looking for readings that cause the computer to think the engine is extremely cold.

If that checks out ok, you're going to need to do a base idle reset procedure.
http://www.muscularmustangs.com/idlereset.php

macdaddy1989

thanks i am going to try that. ill let you know what happens. thanks again

macdaddy1989

it was the ECT. it also caused the car to not crank very well after it was warm. thanks. that saved me alot of money. i was about to buy a MAF and o2 sensors.

mjr46

next time try running a koer test and pulling codes, and that will save you alot of time

macdaddy1989

can you explain to me what a KOER test is?? and since i change the ECT, do i have to check the voltage on the TPS as well.