A little more help needed

[moosemeadows]

Ok here we go onto my next issue. 87 Bronco ll 93 explorer 4.0 swapped quite a few years ago. Started running poorly developed a higher than normal idle 1500-1700 found a leaking plenum gasket replaced that along with ISC because it was a little wonky when tested. No weird codes pertaining to engine issues. Sprayed carb cleaner all over, that's how I found the plenum issue and a leaky PCV hose and valve, and fixed that stuff. Now it runs after frame fuel pump replacement but still idles higher than normal 1200-1400 normally idled around 900-1000 for years. Disconnected throttle cable MAF and ISC no change. Checked all around the vac tee removed hoses and plugged connections no change. Have tested the TPS and within specs. Took throttle body off plenum and replaced gasket & cleaned because of a poor connection on the air tube from MAF to throttle body and cleaned MAF with proper cleaner. Sprayed more carb cleaner and no leaks or change noticed. Any suggestions thoughts and advice gratefully appreciated. Thank you in advance.

 

[scotts90ranger]

What's it idle at with the idle air control solenoid unplugged? It should be like 500rpm, if it's not I would back the throttle stop screw out until you get close to there... it could just be running better than it has in a while now that it isn't dealing with as much unmetered air...

 

[moosemeadows]

What's it idle at with the idle air control solenoid unplugged? It should be like 500rpm, if it's not I would back the throttle stop screw out until you get close to there... it could just be running better than it has in a while now that it isn't dealing with as much unmetered air...

Sir thank you for the reply and the suggestion. It didn't drop at all even after disconnecting the MAF with the IAC still disconnected still no change. My question is why would the position of that screw change when I'm the only one working on it and I haven't changed/adjusted it? Not being disrespectful but trying to make sense of that. Thanks again.

 

[scotts90ranger]

Because you fixed the unmetered air leak when you fixed the intake manifold gasket, that was causing it to not run right (MAF systems hate air that doesn't come through the MAF), over time they can compensate with the O2 sensor and get the fueling close for what is going on but chances are it wouldn't idle right so at sometime previous the idle screw has been screwed in bypassing the control of the IAC or the IAC is stuck open causing a high idle.

Whatever you have going on is beyond normal operation so there's air coming from somewhere whether it be from the idle screw or the IAC stuck...