engine racing at idle
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Junior User
Joined: May 2003
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engine racing at idle
Help!
'91 F150, 302 engine...
Engine normally idles at ~700 rpm. Lately it's been
erratic and idling rather high. Now, it's racing at idle,
sometimes as high as 2500 rpm. When it gets that high
the check engine light comes on, though I don't know if
this is a symptom or a cause.
Coming back from lunch, I could drive it only with the
clutch and the brake, no accelerator needed.
Thanks for any help you can give, regards, Cliff
'91 F150, 302 engine...
Engine normally idles at ~700 rpm. Lately it's been
erratic and idling rather high. Now, it's racing at idle,
sometimes as high as 2500 rpm. When it gets that high
the check engine light comes on, though I don't know if
this is a symptom or a cause.
Coming back from lunch, I could drive it only with the
clutch and the brake, no accelerator needed.
Thanks for any help you can give, regards, Cliff
Postmaster
Joined: Dec 2003
Posts: 2,659
Likes: 2
From: S/C Texas
If its intermittent, I'm gonmna guess and say you need to remove the automatic choke and replace it with a manual. If kicking the gas pedal sometimes fixes it, I'd put my $ on the choke. I would start by checking the codes.
Senior User
Joined: Dec 2003
Posts: 354
Likes: 1
From: Memphis, TN USA
If applicable, I'll say bad TPS.
The TPS is the most overlooked sensor with regards to erratic IDLE problems. Be careful when squirting cleaner solvent in the throttle body because the TPS will "fail" if it is saturated with that cleaner solvent.
Never attempt to clean the TPS with any chemical because you can't clean it and if you try to clean a good TPS then it will "fail". TPS is cheap so just replace it.
If applicable as well, it does not hurt to remove and clean the IAC and the spot where the IAC goes in.
The TPS is the most overlooked sensor with regards to erratic IDLE problems. Be careful when squirting cleaner solvent in the throttle body because the TPS will "fail" if it is saturated with that cleaner solvent.
Never attempt to clean the TPS with any chemical because you can't clean it and if you try to clean a good TPS then it will "fail". TPS is cheap so just replace it.
If applicable as well, it does not hurt to remove and clean the IAC and the spot where the IAC goes in.
Lead Driver
Joined: Nov 2002
Posts: 9,557
Likes: 44
From: Concord, NC
No choke, automatic or manual, on a '91 since it is fuel injected. You said the check engine light comes on when it does this. That means that there should be a code stored in the computer. Start with pulling the codes and go from there. It sounds like there is a vacuum leak. Look around and see if there are any loose or cracked vacuum hoses.
Last edited by EPNCSU2006; Jan 8, 2004 at 08:40 PM.
Thread Starter
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Junior User
Joined: May 2003
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Last night I took off the throttle body so I could get
the TPS out. Don't have the equipment to do the codes...
I do susspect the TPS, and the gasket between the
throttle body and the intake was torn and in bad shape.
But there is something else wrong here. Oil is getting
into the intake! How could this happen?
Thanks, Cliff
the TPS out. Don't have the equipment to do the codes...
I do susspect the TPS, and the gasket between the
throttle body and the intake was torn and in bad shape.
But there is something else wrong here. Oil is getting
into the intake! How could this happen?
Thanks, Cliff
Lead Driver
Joined: Nov 2002
Posts: 9,557
Likes: 44
From: Concord, NC
You can check the codes with a paper clip. The oil residue in the intake is from the EGR near the front and PCV near the rear of the engine. I would test the tps before replacing it so you can be sure that is the problem.
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