very high idle
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Freshman User
Joined: Dec 2003
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very high idle
hello all,
i have 91 f150 2X4 w/auto. the problem is after the engine warms up the idle will jump to around 2000 to 2500 rpm. i replaced the IAC and it still does the same thing.
can someone please list the items that i need to do to determine what is causing it to do that.
all information will be helpfull
thank you
faceman
i have 91 f150 2X4 w/auto. the problem is after the engine warms up the idle will jump to around 2000 to 2500 rpm. i replaced the IAC and it still does the same thing.
can someone please list the items that i need to do to determine what is causing it to do that.
all information will be helpfull
thank you
faceman
New User
Joined: Mar 2003
Posts: 13
Likes: 0
From: New Brunswick
Gee, seems to be a common problem lately. I have a simliar problem with my 92 1/2ton. Only mine starts out at high idle and stays on high idle (1600rpm). There are a couple of other threads on this same issue in this folder. One started by me and the other by uncle Bob. (page 2). Some other forum members gave us both some good ideas. Have a look at them too. Good luck. It seems to be a tricky problem to solve.
Posting Guru
Joined: Nov 2003
Posts: 1,341
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From: Detroit Subs
Re: very high idle
Originally posted by faceman1
hello all,
i have 91 f150 2X4 w/auto. the problem is after the engine warms up the idle will jump to around 2000 to 2500 rpm. i replaced the IAC and it still does the same thing.
can someone please list the items that i need to do to determine what is causing it to do that.
all information will be helpfull
thank you
faceman
hello all,
i have 91 f150 2X4 w/auto. the problem is after the engine warms up the idle will jump to around 2000 to 2500 rpm. i replaced the IAC and it still does the same thing.
can someone please list the items that i need to do to determine what is causing it to do that.
all information will be helpfull
thank you
faceman
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Freshman User
Joined: Dec 2003
Posts: 36
Likes: 0
this is what i know,
when i put it in gear it stays high, it drops only a little to around 1500-1800 rpm. what i have noticed is that the green plastic vacuum line from the egr soleniod was not connected to the egr but to a vacuum port on the intake. i rerouted it and it is still doing the same thing. is there a way to check the soleniod to see if it is working correctly.
to me it seems that something is tell the computer to tell the IAC to open up and stay there after warmup.
i will try some of the other tests that my book says and ill let you guys now what was the result
thanks
faceman
when i put it in gear it stays high, it drops only a little to around 1500-1800 rpm. what i have noticed is that the green plastic vacuum line from the egr soleniod was not connected to the egr but to a vacuum port on the intake. i rerouted it and it is still doing the same thing. is there a way to check the soleniod to see if it is working correctly.
to me it seems that something is tell the computer to tell the IAC to open up and stay there after warmup.
i will try some of the other tests that my book says and ill let you guys now what was the result
thanks
faceman
Senior User
Joined: Aug 2003
Posts: 122
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From: kansas
A bad tps will cause a high idle. If you unplug the idle air motor and engine dies that will tell you if all the air going into intake is giong in thru idle air circuit. If engine doesnt die then air is grtting into intake somewhere else. If tps reads too high, computer will hold idle motor open too far. Another thought, idle motor could be stuck open. If engine doesnt die when idle motor unplugged, cover intake openings with hands and see if that will kill engine. good luck
Senior User
Joined: Jan 2003
Posts: 169
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From: Florida
I had a almost the exact same problem on my Bronco. Wound up being the TPS sensor. Pretty cheap and easy to fix. Idles like a champ now. Or did till I blew a head gasket, anyway.
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Posting Guru
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From: Detroit Subs
Originally posted by circledirt
A bad tps will cause a high idle. If you unplug the idle air motor and engine dies that will tell you if all the air going into intake is giong in thru idle air circuit. If engine doesnt die then air is grtting into intake somewhere else. If tps reads too high, computer will hold idle motor open too far. Another thought, idle motor could be stuck open. If engine doesnt die when idle motor unplugged, cover intake openings with hands and see if that will kill engine. good luck
A bad tps will cause a high idle. If you unplug the idle air motor and engine dies that will tell you if all the air going into intake is giong in thru idle air circuit. If engine doesnt die then air is grtting into intake somewhere else. If tps reads too high, computer will hold idle motor open too far. Another thought, idle motor could be stuck open. If engine doesnt die when idle motor unplugged, cover intake openings with hands and see if that will kill engine. good luck
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Tuned
Joined: May 2003
Posts: 454
Likes: 1
From: College Station TX
I had the same problem with my truck and it turned out to be the upper air intake gasket. It's hard to find, but a good shop can put a smoke machine on it and find ou twhere the vaccuum leak is. The gasket is cheap but plan on about 3 hours of labor if everything goes well.
Senior User
Joined: Jan 2003
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From: Florida
Along those same lines, I've Heard that if you take a propane torch and turn the gas on (without lighting it, obviously) you can run it around the vacuum lines or intake gaskets and if the idle goes up it indicates a leak. Now I've never tried this, it's just something I remember someone talking about. I'd try to get some more input before I tried it, but if it works it'd be an easy way to diagnose vacuum leaks yourself in your own garage.
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Freshman User
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i checked for a vaccum leak and there was nothing so i am probably going to go ahead and replace the tps. by the way i am also experiencing a bad shifting problem. it has a E4OD and it doesnt want to shift right. takes forever to change gears. i had autozone pull the codes and the only ones they got were 121 and 628 any thoughts
thanks
faceman
thanks
faceman
