89 Ford Bronco II Fast Idle

[oneosufan]

I have an 89 Ford Bronco II that I am having idle problems with. It likes to idle around 1100 rpm. The idle set screw is backed all of the way off. If you are driving and you engage the clutch and get out of gear it likes to idle around 1500 to 2000 rpm until you come to a complete stop and then it will idle back down to 1100 rpm. I have replaced the TPS and the Map sensor. I have cleaned out the throttle body with carb cleaner. I have also cleaned the air intake sensor that is on the side of the manifold. I have ohm out the sensor and it ohms at 11.3. Does anyone have any suggestions for me. I dont think that I have a vaccum leak anywhere but I am not for sure. Help Please.

FYI The engine is a 2.9 liter fuel injected

 

[Dishtowel]

Did it just start doing this out of the blue? was it good before? I had idle grief due to throttle cable adjustment, and due to the airbypass valve being plugged, (idk if the 2.9 has the air bypass though)

 

[oneosufan]

Yes, it started about a month ago. I have checked the throttle cable and I do not see any kinks or abrasions

 

[dusto2]

i would hunt around for a vac leak or possible iac valve sticking

 

[mjonesjr]

Also check to make sure your fuel pressure regulator vacuum line isn't off. mine high idled when I changed the plugs; i had knocked the fuel pressure regulator vacuum line off.

 

[WildSide]

First of all that screw is NOT for idle adjustment it is for setting the TPS to spec. So you messed up and will have to readjust it properly.Unless you have leaky intake gaskets or vaccum leaks (check you brake booster as well) then your IAC needs cleaning or replacement. Also make sure that your coolant level is up and that the temp sensor is good otherwise the computer will think the engine is cold and will adjust the fast idle acordingly.

 

[lil red]

if your breaks work ok its not from the booster
but i agree sounds like vaccum

 

[mkpecor]

your throttle positioning senser is probly bad. my truck was idleing up and down. got the new senser and its all good now, take it to shmucks they will plug it therereader and tell you.

 

[oneosufan]

I think that it is an intake leak. I sprayed carb cleaner around the intake and the idle dropped alot. Thank you guys for all of your suggestions. I will be working on it this Friday. I will let you know if that fixed my problem.

 

[WildSide]

Don't forget to get a volt meter and reset the TPS screw

 

[philzilla]

maybe clogged fuel filter, probly not but it couldnt hurt to change it out, alot of lower grade gasses clog up easier