Throttle body problems?

jrt2nd

jrt2nd

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Supporting Member
Joined
Apr 30, 2019
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37
Location
Colorado Springs, CO
Hi all. My wife's TJ has an occasional miss and sometimes a stall when its cold. Sometimes when she first starts it in the morning it will stall when she puts it in gear. We have taken to reving it up a bit before we put it in gear. It also has a slight hesitation when we first step on the gas when its cold. I was under the hood today trying to figure out the problem and I noticed if I pushed or pulled on the butterfly valve shaft (without turning it) it would change rpm and sometimes even stall. I could not detect any play in the shaft but I could definitely make it change rpm. Is it possible I need a new throttle body? Or could it be something else like the TPS? Can these throttle bodies be rebuilt; as in replace o rings or something? Once the vehicle warms up it runs fine.
 
Sounds like there's a good chance the IAC (idle air controller) could just be dirty. The IAC is what provides all of the engine's air when at idle rpms. That's cleanable by just spraying an aerosol throttle body cleaner into the throttle body while the engine is running at idle rpms. The IAC will suck the cleaner in through itself so long as the rpms aren't raised above idle. When the engine stalls that's normal. Just restart it and then do it again. I try to get 1/3 of the can through the IAC.

That could also be caused by a bad TPS (throttle position sensor) which is attached to the throttle body.
 
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Just went through this sort of issue except my was opposite of yours. My idle was sporadically high even after the engine had fully warmed(sometimes would idle at 1300-1500RPM). Several times I cleaned the throttle body and IAC and even replaced the IAC with no results. Very similar to what you just said i started playing around with the throttle plate while it was closed and caught it in a moment of high idle and found by pushing down on the throttle plate it brought my idle back down to normal. As Jerry mentioned about the TPS sensor and it was the sole cause of the issue. It got to the point during diag. where I would tap on the backside of the TPS sensor and my idle would fluctuate up and down. Just sparked a thought when you talked about moving the throttle plate around. GOOD LUCK!
 
If the above advice does not yield the desired results. Start by checking the basics in the fuel and ignition systems. Filter, plugs, etc. Look carefully for vacuum leaks. Oddly enough, the speedometer gear not working would cause mine to stall. I replaced my IAC and TPS as preventive maintenance items, cheap and easy to do. Saved the old ones as spares. Frivolous? If I never have an issue I'll chalk it up to OCD maintenance habits. Money in a Jeep beats money in the bank.
 
Chuckle. I like that! (money in a jeep...) Well, it turned out to be the TPS. I had replaced it back in August when I had a stalling problem that turned out to be a short in the computer. I had replaced it (before reading Jerry's advice) with a cheap one from Ebay. So I put the old OEM one back in and it runs like a charm now. Thanks for the advice!
 
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