Just recently I undertook the task of replacing the head gaskets on my 99 ranger 3.0 Went to start it. It started just fine but it idles too high even after being warmed up. Replaced the dpfe sensor. dsiconnected the main vacuum and plugged it still idles high. unplugged idle solenoid still idles high. Dsiconnected the vacuum to the egr too. Its got me stumped. i really need some advice its driving me nuts.
Thanx

 

Idle on EFI engines is set by air flow into the intake, restricted air flow = lower idle.
That is how the IAC(idle air control) valve works, it allows more or less air past the throttle plate.

If idle is high with IAC valve wires unhooked then you have a vacuum leak.
If you have blocked off the PCV, power brake and smaller vacuum lines then leak is in the upper or lower intake gaskets.
You can spray soapy water around intake to see where idle is effected, or carb cleaner.
I often remove/loosen fan belt when doing this, cold engine, so fan doesn't effect where I am spraying, you can run a cold engine a few minutes without water pump.

I would also check the throttle plate, make sure it isn't stuck open a bit, i.e. held open by throttle cable or cruise control cable.

 

IAC valve wires disconnected and no change.

 

Yes, you probably got a bad seal on lower intake gasket, maybe upper.

 

Ok one other detail I neglected to mention thinking it might not be related but it has this loud buzzing like when im at idle it will drown out the radio but when i accelerate it drops off. My question now is the buzzing and high idle related? The sound is coming from under the upper intake if that helps. Thank you to anyone that can help or add more advice. The advice so far is great.

 

Vacuum is highest at idle/low RPMs then drops off as RPMs get higher, so yes what you hear could be a vacuum leak.

There is a 'smoke machine' that is used to find vacuum leaks.
Smoke is pumped into a sealed intake and if there is a leak somewhere the smoke will come out.

I prefer a good cigar and a glass of bourbon, but I am cheap, some "feel" the bourbon is not required, I "feel" sorry for those people, lol.

Remove air plenum, big air tube, and block off the intake at the throttle plate, saran wrap works.
Use the PCV valve hose inlet on the intake, put a longer hose on it if needed.
Light the cigar(cigarettes don't work) puff it up and blow smoke into hose, continue until intake is full, you should start seeing puffs of smoke coming out of any leak points.

 

hehe ill try it.thanks

 

Update. Tonight i used the smoke method with a cigar 2 for 89 cents btw, and low and behold it was puffing out the bottom of the throttle body. Apparently i had neglected to properly clean both surfaces of old gasket material causing air to get sucked in between the throttle body and upper intake the new gasket acted like a reed vibrating with air flowing over it,IE a high pitched buzz. Runs and idle a heck of alote better. One question though how long does it take to relearn the fuel trims after it has been running with the vacuum leak? Any suggestions will always be appreciated and thanks to all that have helped and thanks for having a great site!!

 

It can take 3 or 4 heat and cool cycles(at least 15 minute drives), for long term fuel trim to show the changes.

Unhooking the battery, for 5 minutes, can clear short term memory and force computer to relearn some parameters.

Also you may have to stick a "patch" inside the air cleaner housing, NicoDerm, since intake has taken up smoking, lol, don't want withdrawal symptoms.

 

So, did you manage to finish up with that 89 cent cigar? No point in it going to waste, LOL.