I have a 99 Ranger w/3.0. It idles about 1500 rpm cold,and 1200 warm. Here are the things that I have tried.
1.Checked ALL vacumn hoses/lines
2.Changed Air idle control sensor
3.Throttle position sensor
4.removed and completely cleaned throttle plate in throttle body.
5. removed top of intake manifold and checked for cracks and/or leaky gasket.

Nothing seems to change. Could it be a faulty ecm?

 

You've been busy on this one. Could be a number of things, but a faulty ECM doesn't belong very high up on your suspect list, as they rarely fail. Do you have a lit CEL, or have you had the computer scanned for pending, or set trouble codes & if so, post up All trouble code Numbers, as they can offer up good trouble shooting clues.

High idle speed is usually caused by a vacuum leak somewhere, or a mechanical problem like a faulty or dirty sticking open IAC, or throttle plate as you suspected, but can also be caused by out of spec fuel pressure, or leaking fuel injectors, or something as simple as a dirty stuck open PCV valve, or a crack in its rubber hose or fitting, as its down stream of & not monitored by the MAF sensor it can cause idle woes, so you may still have some more basic trouble shooting to do.

If you have, or can come by a scantool that'll read live PID sensor feeds to the computer, have a look at fuel trim, O2 sensor switching range & speed, MAF, IAT & ECT sensor PID's & post the Numbers so we can see if they're offering up some clues as to whats going on & maybe where.

Perform a running & off fuel pressure test to see if pressure is holding, at the under hood fuel rail schrader valve test port & post the numbers.

 

I appreciate the response. I have checked the pcv and it's ok.I suspect highly that it's sucking vacumn somewhere(I can't hear or detect it)because it is running very LEAN.Ipulled the plugs and found them burning very white and has lots of white chalky buildup on the tips of plug. It will run smooth for 100 mi. or so ,then start burning the plugs up. Unfortunately,I dropped the truck off at local technician w/scanner 2 weeks ago,yesterday I stopped by to see if he had got a chance to look at it,and his wife sadly informed me that he had passed away a few days earlier unexpededly. So I will go get the truck today and find someone w/scanning tool.

 

I have been chasing this vac leak around for a long time now. I have a high idle condition. I pulled codes for IAC overspeed, canister purge valve, and lean on banks 1 and 2. Pretty much screams vac leak.. I am also getting bad MPG (8-10).
I have replaced the IAC valve, PCV valve, and a few vac hoses that looked old. No change.. Seems to run better w/ IAC unplugged, but the wires and valve all check out good...
After the charcoal canister and valves, there is a vac hose that connects to a hard line, which runs back to the gas tank, correct? Here's my main question... If that hard line is leaking somewhere between the gas tank and purge valve(s), would that be enough to pop all three of those codes or even cause high idle? Could it just be the valves/sensors connected to the canister, and how can I test these? Where to go from here.... Please Help!

 

If either of you suspect a vacuum leak but can't find it, maybe consider trying a smoke test, by loosening the brake booster vacuum line & blowing smoke into it & watch for signs in vacuum lines, or intake manafold gaskets.

 

Thanks Pawpaw I will try that! I have tried before with a cigar but I wasn't sure where the best place to blow the smoke in would be. I tried a few lines with no luck. Hopefully the brake booster line will give me some direction.

 

The brake booster is a larger diameter line, that hooks directly into the intake manafold, so you should be able to blow a good amount of smoke through it & maybe have a better chance of finding a vacuum leak. Let us know what you find.