i have a 1999 ford f150 4x4 xlt with a 4.6 vin w romeo, and a 5 speed trans. it has about 97000 miles on it. it is my first ford. i love it, but as of late it has been developing problems with the idle. when ever i push in the clutch it revs itself up to 2000 rpms and sometimes higher and it stays there until i punch it to the floor. sometimes i have to shut the truck off. then it is fine for 2-3 gear changes then it idles high again.i was thinking vac leak or bad sensor? can anyone help me or suggest the possible source of the problem.

 

I'd bet it's the throttle position sensor (TPS).

One going out will do exactly that.

 

Disconnect your battery to reset the KAM, clean your IAC and then let it idle for 15 minutes. For ½ the idle time turn on your A/C so the PCM can learn the idle with A/C on.

Regards

Jean Marc Chartier

 

It's not the TPS, most likely.

It's probably the IAC sticking. They gum up and the computer can't properly regulate idle speed. Extremely common on most Fords.

Cleaning them sometimes helps, usually replacement is necessary.

As for the idle reset, just reset by disconnecting the battery as noted. It only takes a minute or two to get a decent baseline idle strategy to be implemented.

Start the engine with all possible loads OFF. Let it idle for 30 seconds, then start applying loads such as the A/C, blower, headlights, stereo, turn the steering wheel 1/2 turn in each direction, then drive off. "Normal" driving is all that is required.

Steve

 

cleaning the IAC almost always smoothes out your idle...takes literally 5 minutes, 1 flat screwdriver, and some carb/throttle body cleaner.
You may need to purchase a new one however if your old one is bad. They're about 65 bucks.

Do a search on "IAC" youll find pics and info

 

what is IAC where is it located I'm not the sharpest knife in the drawer.

 

Its the little silver canister looking deal on the side of your TB, held on by two small screws (I think 5/16" ?) with a wiring harness coming out the back.

If you need more info than that, as mentioned, search for IAC, there are many many threads on this.

 

Thanks for the tip. I know what I'm looking at now.

 

Bought a new one installed Didnt' help

 

Did you also perform the idle reset?

Check for a sticky throttle plate.

Steve

 

yes done the reset but when I started after reconnecting cables went right back to high idle around 2000 rpm
Is this the norm before turning everything on?

 

thanks guys. took off the iac and it was full of carbon buildup. and the throtlle plate had a bunch on it to. i also ran a BG intake cleaner service at work today. it is a fuel treatment we sell at the dealership i work for. that stuff works awesome. truck is running great (other than the spun connecting rod bearing).

 

You went out and bought a new one, installed it, and reset the ECM, all in the two minutes between your two posts? I'm impressed!

 

Also impressive since he hadn't asked for nor was given advice for his specific issues (whatever they might be).

Steve

 

No doubt! Not bad for a dull blade. lol.