Throttle sticking

Hammer24

Hammer24

TJ Enthusiast
Joined
Jan 29, 2019
Messages
428
Location
Melbourne, Australia
Hoping someone can help diagnose my latest problem, had an idling problem so ran some throttle body cleaner through the throttle body at idle and also above idle to make sure everything’s cleaned. It fixed the idle bUt on the drive to work this morning (first drive since fixing it) I found the throttle was sort of sticking. I don’t think it happened until I’d been driving for a few minutes but what was happening was I’d take my foot off the throttle and it would act like I still had my foot on it for another 2-3 seconds. Thinking possibly TPS or vac leak but not sure why this would only happen after cleaning the IAC/TB. Cheers
 
The throttle plate or cable is probably just binding. When you pull the cable at the throttle body does it snap closed? Does the pedal feel completely normal, can you feel the throttle plate snap shut when you release the pedal, do you hear a nice solid click as it closes?
 
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Throttle feels like it’s working fine from both the pedal and the cable to the throttle body, and it’s returning to the idle position fine. Can’t hear anything off so far but will have a closer inspection when I get home from work.
 
Also check that the cruise control or hand throttle (if equipped) cable isn't causing any binding. Spraying the throttle lever and any associated cables with lubricant should temporarily alleviate anything.

I have had the throttle stick slightly when the cruise control cable bound against my hand throttle cable, but fortunately I was able to cycle the hand throttle and take care of it. I didn't even notice until I was completely stopped and running 1500 RPM. Clearancing the hand throttle cable from the pedal cable and the cruise control cable permanently solved the problem.

I wouldn't think it would be likely that the TPS would cause the issue, since the engine would run like total crap in the brief time it gets next to no air but a lot of fuel. I would think the IAC would be suspect, as it could let in unintentional air.

I believe the later Jeeps have deceleration fuel cut-off (DFCO), which could potentially cause a minor "stuck throttle" feeling when in gear, as I believe it takes a couple seconds to kick in. If you're in a particular gear running say, 2000 RPM, and you let off the throttle suddenly while holding the gear, there will be a slightly faster deceleration a couple seconds later as the DFCO kicks in. I suspect DFCO only kicks in once the engine is warmed up.

I suspect that's also why a lot of TJs make the "farty" sound when you suddenly let off the gas, but stop a couple seconds later. There are minor misfires until the DFCO kicks in. (This is speculative.)
 
I don’t have cruise control or a hand throttle so that rules that out, also it’s a 2000 which I think is too early to have DFCO which rules that out. I wouldn’t expect it to be the IAC as I’ve just cleaned it all up and it idles perfect. I should’ve also noted that this happens in neutral too but I think only when at speed (I mainly noticed it when shifting gears at 45mph-ish).
 
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On the way home from work it seemed to be fine so I'm a little confused. Only difference i guess was temperature but even this morning it wasn't that cold, at least 40 degrees farenheit, so not sure what to think now.
 
While cleaning the TB did you remove the IAC from the TB or just spray down the throat ? The IAC should be removed and both the seat inside the TB and the disc on the IAC solenoid stem should be cleaned along with the idle air port that goes between the TB throat and the port at the base of where the IAC seats. If not I have seen debris stuck between the seat and disc or on the IAC solenoid stem.
 
CharlesHS said:
While cleaning the TB did you remove the IAC from the TB or just spray down the throat ? The IAC should be removed and both the seat inside the TB and the disc on the IAC solenoid stem should be cleaned along with the idle air port that goes between the TB throat and the port at the base of where the IAC seats. If not I have seen debris stuck between the seat and disc or on the IAC solenoid stem.
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I took the IAC off last time it needed a clean recently, this time I just sprayed straight into the TB at idle as some very experienced members have suggested but either way, I don't see how it can be an IAC issue if the issue doesn't occur at idle and it idles perfectly.
 
Haven't had this problem occur since the first drive after cleaning the TB and IAC, the only thing that comes to mind is when I popped the hood to investigate after that first drive, I noticed the PCV hose looked a little loose, perhaps from pulling the intake off the throttle body, and I jammed it on a little tighter on both ends. Could that have been creating enough of a vacuum leak to result in the throttle sticking?
 
It would "appear" that the throttle was sticking, the RPM's would go higher.
 
Yep it ended up being a vacuum leak, my terminology is a bit lacking in the area but basically my Jeep is not cruise control equipped and the spot where the the vacuum line would come out of for the cruise control is meant to have a little cap on it but mine had come off creating a big leak. But basically I guess for you it could be any vacuum leak.
 
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