I have finished fixing all the codes on my 1986 Ford Bronco with the 5.0 EFI.

But the idle fluctuates just slightly, so I know I am close.
I have already cleaned out the IAC and Throttle body with cleaner.

I found and fixed one bad vacuum hose and will be replacing all the other rubber hoses next. But I have been trying to find a reference for setting the idle adjustment screw on the throttle body.

This is what I set it at but wanted to verify if it is correct or not.
With the adjustment screw backed off, inserted a .010 feeler guage, and tightened adjustment screw till feeler guage was tight. Then adjusted the TPS sensor to .98V with the key on at idle.

Thanks Guys,

Harlow

 

There IS NO ADJUSTMENT on the throttle plate stop screw. It does NOTHING more than keep the throttle plates from sticking in the bores. It has nothing to do with idle air control. All of that is handled by the IAC and running the stop screw IN only messes with the IAC's ability to properly control idle air. IF the stop screw has been run in for any reason the only "proper adjustment"( and I put that in quotes because there is no adjustment listing for it) is to start the truck and run til its at normal op. temp. Once at operating temp., the IAC must be electrically disconnected with the engine running. A properly functioning IAC will then close and the engine will sputter and die within a couple of seconds. If it does not, make certain there are no other vacuum leaks, then back the idle stop screw OUT until the engine does die. Turn the key off, disconnect the battery for about 10 minutes to clear the IAC fault code(s), then reconnect the IAC and the battery.

 

Well before I messed too much with the idle, I pulled out my vacuum guage and checked the rest of the vacuum lines. With all those replaced it ran smoother with no fluctuation. Some of the old rubber lines were hard and dry on the ends.

So after good results with fixing any vacuum leaks I deceided to recheck my Throttle Body and TPS. With the engine warmed up and the IAC disconnected it stalled within a few seconds. Put the key in the on position, and rechecked the TPS. It looked fine so I disconnected the battery and 20 minutes later, drove it down to get some lunch. It drove well so It looks like I did not mess anything up with the throttle body.

Thanks for the help,

Harlow

 

Cool, glad to hear it. I have heard nightmare stories of trucks that have had the stop screw used to bypass a bad IAC and the results are horriffic since the computer can't control the idle airflow it assumes all sorts of things and it really messes up fuel mileage and other things. Didn't mean to sound like an alarmist there. I have just seen some terrible things happen as a result of the stop screw being "adjusted"