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Old 05-29-2013, 10:47 PM   #1
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Engine Over-reved at stop, now cutting out

I'm hoping someone can give me some guidance on my current problem:
98 TJ 4.0 154,000 miles. Just replaced the battery, fuel pump, and AC relay. Today, while sitting at a red light, transmission in neutral, clutch out, suddenly the engine reved to max RPM's by itself, just for a couple of seconds, then went back to idle. So now, on the way home the engine would completely cut out, just for about a half of a second. It appeared as if everything electrical shut off like I turned off the key. The cruise control reset to off, the gas gauge went to E, all as if the key shut off. Searching this forum it seems like it might be the throttle position sensor (TPS) especially with the over-rev problem happening first, but I'm hoping someone can give me some confirmation on this. No codes, just cutting out.

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Old 05-30-2013, 10:22 AM   #2
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I had problems with my TPS. It created a code though. I went and bought a replacement, changed it out, and started having the cutting out when accelerating. I took the new TPS off, replaced it with the old one, and it ran perfectly. Figure that one out! I posted that just to give you the idea to remove the old, check it out, and replace it to see if that cures your problem. You can't beat the cost of that if it works for you. Just an idea.

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Old 05-30-2013, 10:26 AM   #3
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Yep sounds like a TPS issue.

SpoiledRotten sounds like the terminals inside the connector on yours where dirty/corroded and unplugging/plugging the connection a few times cleaned them up. I always recomend using a light coating of Di-electrical grease in any electrical connectors.
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Old 05-30-2013, 02:15 PM   #4
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Flflash, thanks for the grease tip. I picked up a tube of Permatex dielectric grease when I picked up the new TPS and lubed the contacts before I reattached the connector.

I installed the new TPS and took it for a long test drive, including getting it up to 55 MPH with no problems. So, maybe it's fixed.

Man, I hate it when my Jeep doesn't run, but I enjoy working on it.

Thanks to everyone on this forum for the help!
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Old 05-30-2013, 02:21 PM   #5
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That's a surprising symptom for a bad TPS. Wide-open RPMs makes me think of a major vaccum leak like from a bad seal at the intake manifold or similar. The TPS only tells the computer what position the throttle is at, it can't actually let in the the high volume of air that would cause high rpms.
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Old 05-30-2013, 02:38 PM   #6
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I am more used to small motors, but it makes me think of a lean condition and/or air leak. I have had 2 strokes free rev like that and it was usually and intake airleak causing the lean condition. TPS related? I don't know.

Also make sure you don't have something wacky going on with your Throttle cable.

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