Stuck at high rev at start up

[afitzray]

1998 explorer. 98000 mostly babied miles. For the past week, at startup it revs up to about 2500 or so and stays there. For awhile I could turn it off and when I cranked it again it would rev to 1500 rpm and drop to 900-1000 like normal. If i goose the gas it just goes to 3000 and stays there, but the pedal is not sticking at all. When I'm driving and stop at a light it stays at about 1500 but i can feel it pulling and wearing out the tranny. putting it in neutral frees it up to go back to 2500 or so. Any ideas? I feel like its going to be a quick decline for my truck if i can't figure this out.

 

[2000StreetRod]

clean the throttle plate & IAC

Make sure there is a little slack in the throttle cable when the throttle plate is at the closed stop. Clean the throttle body, throttle plate and make sure it freely returns to the stop. Make sure the cruise control cable is disengaged. Clean the IAC valve. Are any diagnostic trouble codes being set?

 

[jchopo01]

Vaccum leak maybe

 

[jremington59]

I'd deffinatly make sure the throttle is going back all the way and not binding.

As was said, clean the throttle body and see if the cruise control cable is releasing all the way.

 

[robertoa1a]

x2. It can't rev up with the throtle body closed assuming no vacuum leaks and no IAC (idle air control) isues.

 

[celly]

Have you tried disconnecting the battery ground for a while and letting the PCM to reset itself? Sometimes that helps.

 

[afitzray]

Fixed for now. Thanks!!!

Thanks guys for all the help!!! I tried disconnecting the battery for a day and unfortunately that didn't do anything. But, I just finished replacing the throttle position sensor. It was a $30 part from autozone and easy to access so I figured I'd give it a shot. When I took the old one off and compared to the new it was apparent that the old one was a little off. Inside it there is a piece that rotates as it is pushed by the indicator thing on the throttle body, and the old one was not returning to the zero point. It seems to be fixed for now.

 

[2000StreetRod]

Good news!

TPS output should be about 1.0 volts at idle. When you turn on the ignition the PCM reads the voltage and sets that as idle. I'm surprised if it was much higher that a DTC didn't get set. Was the problem the TPS was preventing the throttle plate from closing?

Glad to hear you got it fixed!

 

[robertoa1a]

Have you looked at the throtle body. There may be junk on it.