Oscilliating idle issues

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Apr 15, 2012 | 05:36 PM

LN323

Thread Starter

Junior User

Joined: Dec 2011

Posts: 72

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Oscilliating idle issues

Hey everybody. My van ('90 E-150, 5.8L FI) is having some idle issues. It starts right up, runs well for about 30 seconds, then it has trouble holding a constant idle. It oscillates up and down on about a 6 second cycle (3 seconds to go up and 3 seconds to go down). With no tach yet, I would guess that it revs up to about 1000 RPMs and then drops to about 500 RPMs or something like that. It also dies after about 30 - 40 seconds of this. It also hesitates when starting from a dead stand still at a light. I don't knw if that problem is related or not.

The van's been recently tuned and other than the idle issue, it runs well. I don't know if it's a vacuum leak problem or something else. A friend of mine thinks it might be a idle control unit? I know on my Mazda 323 GT I have a TPS (throttle position sensor). I don't know much about Fords at all (this is my first) and I don't know exactly what it has or doesn't have.

I also don't know if this is a common problem with this vehicle or motor and if there is a quick/easy fix.

Any help is appreciated.

Thanks.

Apr 15, 2012 | 05:56 PM

PStruwing

Senior User

Joined: Dec 2007

Posts: 419

Likes: 2

From: Lakefield Ontario

Check your throttle body and make sure it does not have a build up of carbon, if it is propped open a bit it can cause the hunting idle. Then check and clean the idle control (IAC).

If that does not fix check for vacuum leak.