IAC valve or TPS?? almost crashed.....

justi88 · Sep 20, 2010

Well to start my 5.0 had issues with idle, every time I pressed the clutch the rpms would rise and come down after a few seconds and stay like at 1200 rpms. This problem was causing heating to my car and I don't live in the U.S. so the only solution was adapting an IAC from a ford bronco.

So I picked it up from my mechanic and the idle wasn't totally fixed but it was better, so last night i took for it a spin and gave it throttle until reaching like 80 mph when the throttle stayed open and I couldn't stop the car so I pressed the clutch and the rpms when way up until the red line so i turned the car off and pulled to the side of the road. This scared the .... out of me and I'm really pissed of with my mechanic. :angry4:

So what i really want to know if this is caused by the IAC valve?? If it is I will buy the oem for my car. Please help me out to find out what is the problem... :confused1:

1bad95 · Sep 20, 2010

i would check your timing, pull and clean the tb, iac and mass air. Mine also stuck a few times. cleaned this stuff up, and set my timing back to 10* and never had that problem again

justi88 · Sep 20, 2010

Sorry for the ignorance but I have no idea how to set the timing, could you please explain this to me... also the maf is new from BBK and the IAC has been changed from a bronco..

HISSIN50 · Sep 20, 2010

Is the throttle blade itself (in the throttle body) sticking?

We can't advise driving the car because it's so unsafe, but have you tried disconnecting the IAC electrical connector after the car is warmed up? Does the idle still stick?

Are there any codes?

toyman · Sep 20, 2010

I'm almost certain it's throttle blade, cable or TPS related. I don't see where the IAC would cause that kind of problem. If the throttle blade or the cable isn't binding/sticking check the TPS voltage from closed position to fully open. Closed should be about 1.0v and the voltage should increase smoothly from there to about 4.5v when the throttle is fully open. I'm wondering if while adapting the Bronco IAC to the TB if the mechanic inadvertently did something to the TPS.

justi88 · Sep 21, 2010

I really don?t think he did nothing with the tps, but since the bronco IAC was installed the car really hesitates in the mornings and there is a loud knocking noise that goes away when the car heats up...

I was thinking anyway about buying the oem IAC but I?ll check the the IAC and tps voltage, is there way to know if the cable is worn out???

mustangshane · Sep 21, 2010

Yes, you can move the cable and feel if its sticking without the car running. By pressing it without the car on. Also visually inspect the cable. Its the one with the grey connector on the throttle body. Look in between the strut brace on the top of the motor. Then you can move the throttle slowly and feel for anything hanging up. Might be the throttle body hanging up on itself. Get some throttle body cleaner. Take the rubber air inlet off and spray everything down until it comes out nice and shiny. Spray this stuff into all the holes and orifices everywhere inside the throttle body. Then start it up. It may take a minute for it to start because of all the cleaner in the system. But it'll be ok. I dont see a IAC doing this.

modo · Sep 21, 2010

problem is mechanical. even if the tps failed a wot voltage on the tps isn't going to feed the motor air and the iac bypass shouldn't be enough to feed the motor at high rpm. your throttle body was stuck open

justi88 · Sep 21, 2010

ok I also think its the cable... i see there are two cables beside the throttle body... the cable that opens the throttle is kind of loose, I mean its not very tight, but it looks like its doing its function, is this cable supposed to be very tight??