My 2002 Ranger races between shifts. That is, if I'm driving at 2,500 rpm and push the clutch in to go to another gear the motor may move up to 3,000 rpm with the clutch disengaged.
I have cleaned the throttle plate. No help. I have looked for vacuum leaks but did not fine any. The cruise control seems to be disconnecting normally. I checked for codes with a reader. There were none. The spring closing the butterfly valve seems to be fairly strong. I have pulled up on the accelerator when the engine is racing but it did not help. Any ideas appreciated.


Charles

 

let your foot off the gas?

 

i had a simialr issue, didnt find any vaccum leaks, changed nearly every sensor there was to change, i was down to either the engine control computer (i forget what ford calls the thing) or tear down the top end of the motor to see if there was a bad gasket of somesorts in the intake system that i just couldnt locate earlier. i decided to start taking the intake off, i also had a left valve cover gasket that needed replaced anyways. when i took off the big "air horn" the next part between the air horn and the lower intake is the fuel rail, (at least on my '93 4.0) it turns out the fuel rail gasket had failed at the front and rear, 2 major vaccum leaks, i did pull the lower intake since i was that far along and had the gaskets, but found nothing else wrong. after gettin it all back together it was good as new. that was about 3 years ago. mine too would rev up when i pushed in the clutch to shift, and when i would get back in the throttle to accellerate, it was doggy. i dont know what engine you have, but it could be a simialr issue. vaccum leakage is hard to find sometimes,if it was pressure instead of vaccum you could simply pour soapy water over the running motor, i tried a unlit propane torch, "spraying" the top of the running engine with propane, my theroy as to why that didnt work for me is that the vaccum leak was too big and at the front and rear of the motor, it caused no r.p.m. change at idle while i was "testing" check out post #37 for a picutre from another momber who had a failed fuel rail gasket--->https://www.ford-trucks.com/forums/2...-gasket-3.html again, i dont know what year/motor you have, this may be useless information. also in reading my oringinal posts about my problem, i stated my engine temp was up (due to lean-burn/vac leak) good luck with your soultion, let us know what engine/year it is to help narrow things down a bit more, oh, and welcome to this site!

 

Chas, check your IAC for being gummed up or sticking. The Idle Air Control modulates the rpm by allowing air to bypass the throttle plate. It also opens up more when the engine is cold to get a higher idle. If it is sticky, the rpm will not drop as quickly as you would expect when you take your foot off the gas pedal. You also might not slow down as much as you should when coming to a stop.
You can clean them with 'brake cleaner' in some cases, and in others, replacement is the only solution.
tom

 

I like tomw's IAC idea.

Cleaning mine didn't last, but was a good trouble shooting step for me.

I used CRC QD spray cleaner & no lint foam cleaning tips, or you could use MAF spray cleaner, which are non residual, plastic safe products, that won't get after the IAC little black plastic cap, or it's air filter under neath, or get after the IAC "O" ring seal, or the solenoid windings insulation inside.

More thoughts for consideation, let us know what you find.

 

I agree, My truck did the same thing. Replaced the IAC, and the problem went away.