High Idle 5.0 EFI Problem

[Save-A-Horse]

I've been battling my Bronco all summer long with its' rough running (stalling, idle instability, hesitation). I've replaced the following:
fuel filter, fuel pressure regulator, idle air controller, throttle position sensor, distributor, cap-n-rotor, spark plugs, and coil. I've re-adjusted the timing to 14deg, and re-set the idlle.

Runs great now, accept it idles high (about 1300rpm). I can hear the IAC on, so the computer must be opening the valve. I don't see/hear any vaccuum leaks.

Also, previous owner used a painless wire harness and I'm not sure how to check the codes as I haven't been able to locate the test connectors.

Any ideas what could be causing the high idle?

 

[airbur]

What MAF and injectors?

 

[surfer-b]

Have you unplugged the IAC with motor running, if not try this and see if idle changes, I doubt it will but that's a start. I would bet you have a air leak somewhere, sometimes they are hard to find. The best way I found to detect air leaks is to smoke the engine, you will be surprised at what you will find.

 

[Save-A-Horse]

No MAF (87 5.0), not sure what injectors I have.

If I unplug the IAC, the idle goes down to about 700RPM.

 

[surfer-b]

Do you have the IAC positioned correct, the reason I ask I reversed one on a conversion and it would not work proper, same as what you describe.

 

[Viperwolf1]

What codes do you have?

 

[ransil]

pictures of your engine compartment

 

[Save-A-Horse]

This is the only one I have at the moment, can take more tonight if you need. I think the IAC is hooked up correctly but please take a look. I haven't figured out where the test connectors are, if any, w/ the painless wire harness the P.O. put in (to check codes).

 

[Ourobos]

http://sbftech.com/index.php/topic,1031.0.html

 

[airbur]

IAC is upside down.

 

[surfer-b]

IAC is upside down.

Yeah this is what I was referring to, it happens, it happened to me, walked away from it and come back the next day and it was like a light switch was flipped on, felt like a DA. This pic is the correct way

 

[Save-A-Horse]

SON OF A....
Thanks for the picture surfer-b!

 

[surfer-b]

Need to thank airbur, he posted the pic, I just ask if it was positioned correct.

 

[Save-A-Horse]

nice airbur, appreciate it... heading to the garage right now, nice night for a drive in West Michigan!

 

[Save-A-Horse]

Just back from a nice drive to a new brewery that just opened up... It rode really nice, no idle problems so switching around the IAC worked! The final piece of the puzze, awesome!

 

[airbur]

Sweet. Such a good feeling

 

[eric0o1]

I guess I need to add this to the install manual for the 5.0 harness, would you guys mind if I used your pictures?

 

[airbur]

I guess I need to add this to the install manual for the 5.0 harness, would you guys mind if I used your pictures?

Sure. I can take a better one if you'd like.

 

[eric0o1]

Thanks for the offer but the one you posted is actually a pretty good picture since you can clearly see the connector location being towards the bottom as opposed to being to the top in the other photo that has it positioned wrong.

 

[Save-A-Horse]

I don't mind either. Hope that it helps anotha bronco brotha out!