Wrangler YJ Throttle/Accelerator Sticking!!

[techmonster]

Hello Everyone -

I have:

1995 Wrangler
2.5L I4 Engine
5sp Manual Transmission.

I have seen a few posts online regarding a sticky throttle, but everyone's symptoms seems to be quite varied, so I'd like to post my own if everyone doesn't mind.

This just started suddenly this morning. Two things going on simultaneously:

1. The engine, while accelerating, suddenly sounds like it has been turbo-charged. Ie; when I'm on the gas, there is now a high-pitched "whine", which sounds exactly like the older turbo-chargers we've all heard, with their "whine" sound. When I push in the clutch to shift, the whine decreases, but then increases steadily again once I'm accelerating. It does this in all 5 gears.

2. (More importantly): The throttle/accelerator is suddenly sticking and the engine will race up to as high as 4,000rpm. Specifically:

2a. I'm in gear, accelerating to the next gear. I take my foot off the gas pedal and it stays in place, as if I had cruise control (which I don't), and I keep going down the road at the same speed.

2b. I push in the clutch at this point, and the rpms race up to as high as 4,000rpms. I can step on the break, which does slow me down, but the rpms stay racing.

2c. --> *** If I do a sharp "pop" push/release on the gas pedal, it feels like something that was stuck was suddenly released and the rpms drop down to normal. This does seem to work every time it sticks.

2d. It seems to do this at any gear-level, and at any speed.

2e. I pulled into a gas station asap (rpms were still racing), and shut off the engine. I then restarted the engine, and the rpms were STILL racing. Shut it off again and popped the hood. I found the throttle accelerator linkage, and it looked like it was "extended" (IE; in the position it would be if you were accelerating). I gently popped the back of it with my hand and it physically "released" and popped back into the idle position. I restarted the engine, and the rpms were normal again (until I took off driving again and it did it again, of course).

2f. I have also noticed that if I just start the engine up and just let it idle forever (without driving it anywhere), the RPMs do NOT climb, but rather it just runs at the normal idle rpm level.

* I have read some other posts where someone said their rpms were racing, but that the gas pedal had NOT stayed stuck in position. My pedal DOES seem to physically stay where it was when I release my foot, until I pop it.

* I have also read one post where someone thought that their Throttle Return Spring was missing (not the captive one in the TBI, but the external one that would connect from the throttle linkage arm to the raised bracket above the intake manifold). They apparently asked a Jeep dealer for a spring and were told that a MANUAL transmission wrangler does not have such a spring...(mine, in fact, does not, but I thought maybe it just broke and flew off)

IS THAT CORRECT?

* I have seem posts indicating to replace the TPS (Throttle Position Sensor).

* I have seen posts saying to just get some Throttle Body cleaner and clean the butterfly and related TBI parts.

* have seen a post suggesting replacing the IAC (Idle Air Control).

Considering my symptoms, does anybody have a good idea what the heck is causing this? (Particularly keeping in mind the first symptom #1 listed at the beginning, that being the corresponding sudden high-pitched "turbo whine" sound)

Thanks in advance for any assistance

Brett

 

[Bounty__Hunter]

The turbo whine sounds like a vacuum leak.

The high rpm's sound like a mechanical problem with the accelerator pedal and/or cable. Doesn't sound like its a throttle body or computer issue.

The '95 2.5L manual did not come with an additional throttle return spring, only the spring on the throttle body shaft. You can add another spring but its likely a bandaid fix.

Remove the airtube and throttle cable from the throttle body. Look into the throttle body while you move the move the throttle arm by hand, opening the throttle plate. See if you can feel the throttle plate sticking or not moving smoothly.

 

[Poop3000]

turbo whine could also be coming from throttle body, but the vacuum leak is worth checking out.

if you decide to clean your throttle body, i strongly recommend the seafoam brand throttle body cleaner (not the fuel treatment, although that's also a great product).

 

[techmonster]

Bounty Hunter: I did a couple of other tests, trying to figure this out.

First off the stuck throttle: I cleaned the throttle plate and the throttle body walls in that area and tested the sticking of the throttle. Seems to have gone away for now, so I'm thinking the whole TBI assembly needs cleaning (it admittedly was rather gunked up and filthy).

Second, the Tuirbo-Whine: I decided to try to narrow down the problem area (ie; was it engine-related or maybe transmission). I fired it up, put it in neutral, pushed in the clutch to ensure the transmission was NOT in any way engaged, then revved it up. NO whine noise. I then put it in gear: No Whine. I then let out the clutch and started driving: INSTANT Whine, that increases in volume as the rpms climb during normal acceleration. While driving, if I push in the clutch, the Whine Stops. Let out the clutch, Instant Whine again.

(incidentally, the Transmission, Clutch, Master and Slave, and Flywheel were all replaced brand new (transmission itself was actually a rebuild) approximately 11 months ago because the originals all gave up the ghost after 250,000 miles).

This second test tends to make me think it's probably transmission/gear noise suddenly popping up and not the engine. (I am presuming that if there is a vacuum leak somewhere, or if the alternator, water pump or steering pump were bad that the Whine would have been there as I revved it up in Neutral).

Any thoughts? Am I way off base on my thinking?

Brett



***********************

The turbo whine sounds like a vacuum leak.

The high rpm's sound like a mechanical problem with the accelerator pedal and/or cable. Doesn't sound like its a throttle body or computer issue.

The '95 2.5L manual did not come with an additional throttle return spring, only the spring on the throttle body shaft. You can add another spring but its likely a bandaid fix.

Remove the airtube and throttle cable from the throttle body. Look into the throttle body while you move the move the throttle arm by hand, opening the throttle plate. See if you can feel the throttle plate sticking or not moving smoothly.

 

[jfrabat]

I was gonna say it could be your power steering pump going bad (it whines when it does), but your last post leads me to believe the problem is the transmission or TC. My first advice would be to check all fluids (transmission and TC). From what I have read, rebuilt AX-5's are not so reliable, so it is possible that your transmission is acting up...