stalling out and high idle

[genorater]

i have a 1989 comanche 4x4 5 speed with the 4.0L and when i drive for about 15-20 min it will idle at about 2000 and sometimes stall out and when it stalls it is hard to get it goin it almost seems like it is not gettin fuel, i have to keep hitting the gas even thoe it is fuel injected i have replaced the IAC,TPS,fuel pump,fuel filtter,PCV valve,spark plugs,crank position sensor,02 sensor,MAP sensor and it is still doing the same thing. If anyone has any ideas on how to fix it and what parts i need that would be great thanks :cheers:

[Wildman]

Did you ever do a fuel pressure test???

 

You already changed out just about every sensor in the engine bay ;)

 

But did you ever check the fuel pressure regulator???

 

See JT's write up......Here

[genorater]

i did and it is at 35 psi and when i shut it off she goes up to abput 40 and stays there and yes i also changed the fuel pressure regulater :dunno:

[maddzz1]

Did you try cleaning the throttle body when you were changing the iac. Maybe it is sticking. You could also have gotten a bad iac. i remember reading that the pintle in the iac is quite sensitive.

[genorater]

ya i replaced the iac and i took the throttle body right off and took a toothbrush and brake cleaner to it 4 about an hour

[Pete M]

Brake cleaner should not have been used. Next time use a throttle body cleaner that is O2 sensor safe.

[jeep guts]

I had a 87' that did the same thing. Iac, its more than likely the problem, of course cleaning it with brake clean can't be good, just to many sensitive parts down stream from it. You may have wipedout another sensor because of it. Experience has taught me to use the right stuff or you can do more damage that good. Reclean with injection cleaner, and try it.

[genorater]

i will try that but i cleaned it like a month ago and it still runs the same . when it is cold it runs good but when it warms up it starts to idel high and then it will stall out :dunno: don't no what to do or what to check i have almost replaced every sensor and the fuel pump and regulateraswell sa the filter

[maddzz1]

The fact that it runs fine until warm leads me to believe it is your O2 sensor since it will run in open loop mode until it warms up and then start getting info from the O2 sensor.. That with the fact that you cleaned the throttle body with brake cleaner which from what Pete wrote sounds like it could have damaged the O2 sensor

[genorater]

well today it was messin up on me and now it has sat for about 3 hours and i just went out to start it and it started no problem . drove around the block and it was idling at about 1200 I'm completely stumped :fs1: :fs1: :fs1:

 

and what would happen if i ran it without the 02 sensor pluged in???

[maddzz1]

Not positive but I think once it warmed up it would run horribly, if at all, since the O2 sensor tells the ECU which/how much fuel to air mix.

 

Try it and if it runs about the same as it does now it is a good sign it is a bad O2 sensor. the high idle still leans toward a bad iac. I think i remember reading a while back that someone replaced the iac and the problem persisted. turned out the new iac was defective. Once they returned it for another one the problem was solved. I would return that iac for another one.

[BLHTAZ]

One thing that has not been mentioned (that I see) is the CTS (coolant temp sensor). It is located in the left side of the block and it does have a pretty direct impact on how the engine runs.

[jeep guts]

Does the motor run ok at upper rpm when it warms up? Is there at any given time, that it runs ok? Even if it's short lived. If you unplug the o2 sensor, it will stall at startup, then restart and should stay running, just bad on gas mpg.