Runaway throttle?

[gr8dain]

Got an issue with my CJ. It is a AMC 258 i6 / 4.2l with a 4 bbl Holley.

Last week on my commute home, I was crawling in traffic and my engine decided to rev up to 2,000 rpm. It would only go down if I put it in gear, but it wanted to go 25 or so without me touching the gas pedal. After a few miles of messing with that, it went down to 1,500 rpm.* Then a few miles later it went back to normal.

Last night it did it again and went to 2,000. I got home and looked at the throttle linkage while it was idling at 2,000. Did not see anything odd.* Turned it off. Started it and it idles at normal. About 800.

This morning all was good until about 20 minutes into my commute. This time it got to 3000 rpm and was climbing. So I pulled over and cut it off. Then started it right back up and never had the problem again.

It will happen again. I am just wondering if anyone has thoughts.

Fuel pump?

I don't think it is a floor mat but will check. That does not make sense as I was out of it last night when I turned the key to off. Then turned it back on while still out of the Jeep and it was good. And my floor mat is bolted to the floor so it won't move.

 

[Lumpy Grits]

You either have an issue with your throttle linkage(binding or interference)or an intermittent vacuum leak, or both...
Have you checked your throttle return springs?
LG

 

[gr8dain]

You either have an issue with your throttle linkage(binding or interference)or an intermittent vacuum leak, or both...

Have you checked your throttle return springs?

LG

I looked at the return spring yesterday. It seemed normal. And no difference from when it was idling at 2,000 rpm in my driveway and after I restarted it and it was idling at 800.

I will look at vacuum. Did not think about that. I will look at the lines at the carb.

It seemed like when I start on a cold morning and the engine revs high to warm it up faster then relaxes after going a bit. That would be the choke, right?

 

[Lumpy Grits]

Manual or automatic choke?
LG

 

[gr8dain]

Manual or automatic choke?

LG

Auto

 

[mriplaybass]

Check to see that the automatic choke linkages and high idle cams are working freely and not tangled up with a stray wire or vacuum hose, or have a lot of rust on them. Maybe spray some carb and choke cleaner on the choke linkages.

 

[Lumpy Grits]

Check to see if the choke's heating element has broken. If it has, that lets the choke and choke linkage bounce around.
FYI TO ALL-For somedangreason, I'm no longer getting any notifications to posts. I've ck'd my CP and it still shows that I should.......
Have any other posters just start having this problem?
Sorry for the topic 'drift'.....
LG

 

[gr8dain]

I am getting notices via tapatalk but not in email.

Let's see if I can attach a video I just took. Guess not. It happened again. Nothing obvious when I looked at it all. My wire running to the choke looks ok but the black loom around it is melted from the manifold. I will look closer at the wire. But moving it around did not make a difference.

 

[Belizean]

Do you have after market cruise control ?

 

[gr8dain]

Do you have after market cruise control ?

No I do not.

 

[PistolDave]

I have never owned a jeep that still had all of the factory emissions stuff on it so I am not familiar with all the equipment. Are there vacuum solenoids that switch vacuum under certain conditions? Maybe there is a leak downstream of your solenoid such that the leak is only "leaking" when the solenoid is energized? That might account for the problem seeming to occur at random. If the computer controlled carb goes haywire can it cause a wide variation in idle? Just some random thoughts....