Very High Idle Problem

[AutoMechanic]

I have a 1994 Ford Econoline E-150 5.8 V8 and now when you start it up the thing goes full throttle instantly from the start up I have replaced the Throttle Position Sensor, the Mass Air Flow Sensor and the idle air control valve I also cleaned the throttle body throughly and replaced the gasket there. And when this occurs I had my dad look at the flaps on the throttle body and they are staying closed the whole time. I’m not too big of an expert on Ford vehicles but this sounds like something maybe wrong with the PCM or ECM is that what you guys here think it is? I asked my friend who is a Ford mechanic at the dealership and he said he has never seen an issue like this but also hasn’t worked on one of these vans before. I also checked for vacuum leaks which I didn’t find any. I haven’t ever seen a vehicle idle so high ever it sounds about as loud as a plane no joke and I’m scared to drive it since I don’t want it to damage anything. Any help would be appreciated.

 

[t1snwrbrdr12]

It’s relatively common for them to develop a massive vacuum leak behind / under the intake where it’s not visible and you can’t feel it. Have you put a vacuum guage on it to see what vacuum it’s pulling?

 

[AutoMechanic]

It’s relatively common for them to develop a massive vacuum leak behind / under the intake where it’s not visible and you can’t feel it. Have you put a vacuum guage on it to see what vacuum it’s pulling?

No I have not done that yet I don’t have a vacuum gauge at home so when I leave work I will bring mine home with me to check it.

 

[mk378]

Idle goes to about 2500 if the ECM thinks the engine is arctic cold. This can happen if ECT sensor sending wrong reading. Check it with ohmmeter.

 

[AutoMechanic]

Idle goes to about 2500 if the ECM thinks the engine is arctic cold. This can happen if ECT sensor sending wrong reading. Check it with ohmmeter.

Thanks I will check that too

 

[clinebarger]

Remove the IAC valve & place fingers over both IAC holes, Have someone start the engine. (You may have to crack the throttle a little with the other hand to keep it running or to start)

If the engine still races.....You have a massive vacuum leak or the throttle blades aren't closed.

A failed ECT sensor/Open circuit will make it run pig rich.