F250 '90 Engine revs high at idle

[Lex77]

I've been having the engine rev high RPM's 2-3000 at idle. It also seems to do this a little at low gears driving down the road. Almost as if the cruise control is on. Seems to quit in higher gears though. Is my throtle stuck or something else? Any ideas? I appreciate any help on this.

[gtmud]

WHen you start the truck and it idles up, take a wrench and tap the side of the IAC,( a 3" long cylider looking thing with and 2 wire connector) its mounted on the T-body. It will cause your problem. IF after rapping it the idle changes, you just conformed your problem. Either that or look for a large vac leak.

[___Brandon]

I'm having the same trouble with a 92 Bronco with a 302. I have changed the IAC and it fixed it for a while but the problem came back. Is it possible that I need to take the throttle body apart to get to the other side of whatever the IAC hooks into and clean it? Is there some sort of mechanism in there that is getting bound up? Thanks

[birar]

bet my money its the 35$ tps (throttle position sensor ) located on the bottom of the throttle body my 92 f150 had the same problem and so did my uncles and dads all had the same symptoms yours has and that's what it was good luck!(:

[___Brandon]

Ok. I did test the TPS with an ohm meter and it looked ok, but maybe I should just go get one. It sure is annoying when the motor wants to idle at 2800 rpms!!! Thanks for the help.

[birar]

let me no how it works out for ya

[fordtrucksonly]

TPs on the 5 liter mostly controls transmission shifting ... etc.. I would bank on IAC.

[birar]

mine was a 351 my uncles was a 302 tho but ive even seen the same problem with gm cars but it def could be IAC but i was just shareing with what ive seen and tps is way cheaper then IAC and its always been tps when scaning or taking a wild stab at wat it could be by symtoms

[birar]

Originally Posted by fordtrucksonly

TPs on the 5 liter mostly controls transmission shifting ... etc.. I would bank on IAC.

does a 90 even have electronic shift my uncles doesnt uses vacuum and cable and mine is but its a 92 which i be-leave was first yr of the E40od

[dfordski]

Originally Posted by Lex77

I've been having the engine rev high RPM's 2-3000 at idle. It also seems to do this a little at low gears driving down the road. Almost as if the cruise control is on. Seems to quit in higher gears though. Is my throtle stuck or something else? Any ideas? I appreciate any help on this.

This thread is dated 1/08. I fear Lex78 is only a memory (or we are) It's always disappointing when they don't post a follow up! A bucket of Coal for you, sir!

[fordtrucksonly]

Originally Posted by ___Brandon

I'm having the same trouble with a 92 Bronco with a 302. I have changed the IAC and it fixed it for a while but the problem came back. Is it possible that I need to take the throttle body apart to get to the other side of whatever the IAC hooks into and clean it? Is there some sort of mechanism in there that is getting bound up? Thanks

This is dated 12/09, I'm guessing he has the same problem...

[dfordski]

Originally Posted by ___Brandon

I'm having the same trouble with a 92 Bronco with a 302. I have changed the IAC and it fixed it for a while but the problem came back. Is it possible that I need to take the throttle body apart to get to the other side of whatever the IAC hooks into and clean it? Is there some sort of mechanism in there that is getting bound up? Thanks

Maybe run an error code scan and see if it confirms your thinking? The IAC has a couple of ports it mounts against, if it hangs, its within the valve. If you disconnect it at normal operation temp, is the idle affected as it should? Idle drops out and usually stalls. Are you saying the idle hangs high at operating temp? At norn op. temp, remove battery cable for 5 mins. Replace and restart. You now need to reset the IAC perimeters. At operating temp., w/ your foot on the accelerator, have someone disconnect the IAC. the Idle will attempt to stall. catch it using the accelerator & hold the idle at 650-675 rpm. for 2 mins. It knows where it's supposed to be and will stop fighting after 30 seconds or so. After the 2 mins. at normal rpm Idle, shut of the engine and reconnect the IAC. restart & let idle for 2 mins. (should now be at normal idle rpm) shut off for 1 min. Restart, w/ foot on brake, put in gear & let idle for 2. mins. shut off for 1 min. This assumes no active error codes or vac leaks when performed! You & your Idle should now both be in a better place.