89 2.3 idle problem

[homegrownranger]

I still cant get this stupid thing to idle correctly. I replaced the throttle position sensor and idle air control valve and it still does it. they could be bad as well but I dought it. It starts and is fine for the first minute or so then the engine light comes on and it revs really high. then occasionally while im driving it will just idle really low and shut off. I cant figure it out. i checked vacuum and replaced some hoses. what else is there? please help

 

[Mark_88]

I had a similar problem with my 89 Tempo...it was the MAP sensor...the little plastic thing attached to the firewall on the passenger side...you can get them cheap at the junkyard...but they cost over $100 from the dealer...so you should try that...it's an easy enough and cheap enough fix...get two if you can because they tend to be problematic...

If that doesn't help...could be fuel pressure...but that doesn't account for high idle...so maybe TPS or some other sensor...

 

[tomw]

You could pay attention to the CEL being lit up. Pull the codes and see what it is trying to tell you. The MAP sensor will adjust the amount of fuel fed to the engine based upon the load [vacuum inside the intake manifold]. When the throttle is closed, vacuum is relatively high, so it has light load. With the pedal to the metal, the throttle is wide open, and the vacuum inside the intake is very low. The MAP 'knows' the vacuum [Manifold Absolute Pressure] and tells the ECM what the load is. If they go whacky, your idle will be all over the place, but it would run decent at higher speeds, though I think it would use too much fuel.
The engine coolant temp and air charge temp sensors, ECT & ACT one or both could be acting up. When the engine is cold, the ECM will bump up the idle speed by opening up the IAC a bit more. Both coolant temp and incoming air temp are monitored. If they send the wrong information, the ECM will try to fiddle with the idle speed and mix as best it knows how. I think there is a specific ohm's resistance for each depending on temperature. You could remove them and test them using hot/cold water and a thermometer to see if their resistance changes as it should.
tom