My 2002 f150 5.4 suddently started to high idle at 1100 rpm on park and 900 on drive, NO CEL No codes.

So i :
1. Checked for vacuum leaks, none
2. Cleaned the throttle body, nothing
3. Cleaned the IAC and the valve seams to be working, nothing
4. Unplugged the IAC solenoid and the truck died (so Im guessing the IAC valve is not sticking)
5. Dissconected the TP sensor and my idle goes back to normal and perfectly stable (750 on park 600 on drive etc).

Notes:
-To check for vacuum leaks i sprayed every hose with carb cleaner, Tested the infamous pcv tube by plugin it on my pcv valve (which i found to be faulty and replaced) and its sucking good with no sounds or apparent vacuum leaks on the back (idle did come down a bit when plugged but unstable).
-I plugged the IAC vacuum tube and my idle came to 500 rpms


Any ideas? Could this mean the TPS is bad ? The IAC valve i obviously not stuck but could the spring be so worn that its overreacting to the voltage sent by the TPS?

Thanx
Joe

 

Ok I checked the TPS voltage, the pcm is sending a steady 5 volt signal and 12 v ground.
when the throtle plate is closed the signal cable is reading me 1.3-1.2 volts, which is too high, its supposed to be .98, it moves when i move teh throttle plate up till 4.6, , and it kinda jumps but im not sure if its my hand doing the jumping with the thortle cable. When i let it return it wants to go back to .98 but imidiatly it jumps back to 1.3-.2 volts at closed position.

I read on how to test this on a sticky here i think, but it never states anything if your closed throttle position has to much voltage.

Is 1.3 too much? And is it the sensors fault?

Nobody has had experience with these?

Thanx

 

I'd replace the TPS. A Motorcraft replacement is about 40 bucks at rockauto.com. There is a way to get a limited amount of adjustment out of them, but yours is too far off. It shouldn't jump.

 

Replace EVERY hose that came in contact with carb cleaner. They are no longer any good. Replace all sensors as well. Carb cleaner compromises anything rubber and plastic and is meant for cleaning carburetors, not these throttle bodies. You'll burn and melt the ribbon in the TPS.

Just guessing, I bet you tried to clean the MAF with it. Yea, replace that as well. Might want to read the back of the can before hosing whatever down with that stuff. However, Ive heard that it works for removing ear wax, give it a shot

 

jajaj the funny thing is I spent like 300 bucks on everything, hoses the valve everything, i just wanted to know what is causing this! And everybody recommends checking for leaks with the carbcleaner, although hoses seam good... I aslo read somewhere you have to erase teh pcms ram to get a new idle udjuested, that to could be my my culprit since i had a bad fuel pump and the battery discoected for a week...

 

Who's everybody ? Your causing this.

I'd hate to see what it looks like under the hood.

 

Yea, you need to pull your vac harness. First check that it holds vac with a cheap vac tool. Then check that air can move thru. The harness elbows will close making it inoperable. Also the PCV system, specially at the fittings.

The engine has to idle between 700-750 rpms. That's warm idle. Otherwise, there's problems with unmetered air flow and/or sensor readings.

Carb cleaner is nasty stuff, worse than gas. Who ever told you to use this is seriously mistaken, using it in this way will cost you.

Like, I said, if carb cleaner has hit the TPS tap or ribbon entering thru the throttle body, then it's trashed. BUT, the TPS will generate a DTC when this happens, so you may have gotten lucky if you don't have one. Other than that, you'll eventually get DTC's from the fuel monitor regardless.

Also, you'll melt the IAC plunger seals and protective boot. That's not good either lol.

 

lol , Im not kidding everybody recommends it, anyways i replaced every hose and wont use it anymore, i did have a vacuum leak not from the elbow in the back of the pcv but from the pcv itself, it was too loose and the iac when plugged was receiving air from there. Now when plugged and the throttle closed the engine dies, so im assuming leaks are gone... Im gonna change both, the iac and the tps....

 

Another thing, can i drive like 20 miles without the tp to my parts store without frying anything? I know my tranny will kick but besides that?

 

Well, have fun destroying your truck. You won't get help here when you don't listen.

 

Woah, relax im not spaying that thing in my new hoses, Im guessing driving without a tp is out of the question then... I was asking cause i like to install it right outside their store if its a small and easy part and hate the high idle..

 

Ok, This is an example of me being confused,


https://www.f150online.com/forums/v8...uum-leaks.html