engine racing at idle

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Jan 8, 2004 | 02:24 PM

cliffrwarren

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Joined: May 2003

Posts: 66

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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

Jan 8, 2004 | 07:10 PM

peppy

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.

Jan 8, 2004 | 07:16 PM

Slade901

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.

Jan 8, 2004 | 08:38 PM

EPNCSU2006

Lead Driver

Joined: Nov 2002

Posts: 9,555

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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.

Jan 9, 2004 | 09:11 AM

cliffrwarren

Thread Starter

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Joined: May 2003

Posts: 66

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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

Jan 9, 2004 | 09:47 AM

Talyn

Hotshot

Joined: Oct 2003

Posts: 17,791

Likes: 99

From: Ashland City, TN

Replaceing the TPS should fix that problem.

Mine errors out on me a lot.
I have to replace mine. Usually i can just reset it by restarting my truck
I also have a 91.