my truck is an 87 f250 4.9 stick. the only codes the come up are for the computer not being able to control idle (12, 13), thermactor inoperative (44), and evp circuit below blah blah (32). this happened before, it slowly built up to 3,000 and stayed. it bellowed a bluish fuel smelling smoke. a lean code came up, and i changed the O2 sensor (wires were chewed through). it worked fine for 3 days. this morning when i went to start it and it jumped to 2,000. i unplugged tps, iac, o2, steering pressure sensor (individually) and no change. i unplug the vacuum from the map sensor and the idles cuts down to almost normal, but the exhaust is faintly black (too much fuel). i unplug the map and the idle shoots back up (vacuum unplugged or not). throttle blades are fully closed. checked everywhere and havent found any vacuum leaks (i've fixed a bunch when i got the truck). i had the code 32 since i got the truck some 6 months ago. its always had a miss at idle which i figured was a dirty injector since the plugs, cap, wires, and rotor are new. help.

i also pulled the vacuum from the fpr, and the didnt make a difference either.

 

this morning i had the bright idea of starting truck with map, iac, tps unplugged (pulling the vacuum off the fpr just acts like a vacuum leak). it idled at 1,500, and plugging either one of those sensors causes the idle to rise to 2,000. black smoke coming out from the lack of air to fuel. so my assumption is that 1 or more injectors are stuck open or not injecting properly. also i pushed on the fuel pressure fitting with the truck shut off and it spurts a little fuel for a second, instead of shooting out for like 2 mins.

 

A leaking Fuel Pressure Regulator will cause a rich condition. Pushing on that fitting on the fuel rail verifies whether there is fuel or not. Without using a pressure gauge you are wasting your time. With all those sensors disconnected and you still have a high idle that means you have unmetered air entering the intake. Start with checking the FPR, look for signs of fuel leaking past the internal diaphragm.

Get a fuel pressure gauge to verify the pressure and bleed off when shutting the truck off. I still suspect a vacuum leak somewhere in this equation as well.

 

i only pressed on the shrader to give me an idea of bleed down until i got the gauge. i know it wouldnt give me any type of pressure reference. 58#s at idle with vacuum pulled, 48#s with vacuum hooked up (the same reading that i've had since i acquired the truck). a reading of zero as soon as the truck is shut off (last time i checked, it at least it let me watch the pressure drop, haha). i have injectors arriving tomorrow (hopefully) and a fpr as well. its not leaking and works good, but im gonna change it while im in there so i dont have to do it at a later date.

 

Thanks for the clarification!

 

so i changed the injectors with rebuilt ones and the fpr. problem still there. uuuggghhh so last ditch effort i tried to see if the speed sensor would do anything if unplugged, and it came apart. haha when i did unplug it the crazy idle almost stopped. i changed it and viola. while the truck drives better than ever with the new injectors and fpr... i think i could've just did the speed sensor, and been alright.

 

Hi, I have a fast idle to start - on warm days - and settles down to 1050RPM (well it used to ) - now about 1200. Will put tack on it this weekend and try disconnecting sensors as you did, but starting with speed sensor.
Regards

 

the first thing you need to do is fix any vacuum leaks and obvious damage (broken wires ect.). then check your ecm for codes, and go from there. that sounds like a vacuum leak to me. also clean your iac, and check to see if your throttle blades are stuck open a little. my throttle cable was broken at one point and caused the throttle body to stay open a bit sometimes.