Engine/Transmission (1994 - 1998) Runaway RPMs at Idle

[MMcCallie]

The 4KGSK has been in for a few weeks, installed by a diesel mechanic in Loveland, CO. It was too touchy at first and the RPMs would hang on the way down. It was fixed for a couple weeks until tonight.



I'd driven about 6 hours doing over 80 mph much of the way. When i pulled into a rest area the idle wouldn't drop back down to where i had set it, a bit over 900 RPMs. The RPMs kept getting worse until i stopped for the night.



The engine was revving to around 2k at idle on its own, wouldn't come back down when i lifted the pedal. Even locked in 4th gear it kept high RPMs. When i put the transmission in Park or Neutral, the engine revs. The only way to get the idle back down is to put the transmission in gear and hold the truck back with the brakes.



It was too hot and dark to mess with anything tonight, i don't have many tools with me. I've got another 8 hours of interstate to get me home tomorrow. Any suggestions on how to fix this problem? I assume something in the governor is out of adjustment or broken. Will i worsen any possible damage to keep driving it like this? I plan to simply try lowering the idle in the morning.



Any help?

Thanks,

Matt

 

[WShupe]

Loosen them 2-3 clicks on each counterweight.

 

[Signal73]

make sure your throttle cable isnt frayed and binding in the sheath

 

[MMcCallie]

I didn't install the GSK myself. Will i need to remove the AFC or go through the side of the pump? Is this something that can wait to be fixed without damaging anything?

 

[Jim Fulmer]

Pull the AFC and plate out and go through the throat for tiny tweaks like that, just do the same number of clicks on each side. Me personally I would go with 1 click per side. What you are seeing is not unusual with 4K's if they are too tight, plus this will take some of the touchyness out of the throttle.



I set my pump up touchy on purpose then back off were I need too! Another thing you will see if it is set close is the motor might not want to come right down to idle from say 1600 RPM till you put the slightest load on it, even turning the A/C on will be enough load.



Jim

 

[MMcCallie]

It turned out to be something very simple. The nut on the bottom side of the idle adjustment screw had disappeared. The vibrations had also caused the screw to rise vertically so that the idle would not drop. I'd been driving about 80 mph for most of 4 hours so i guess there was time and space for the screw to vibrate that far.

I'd been 4 wheeling in the Rocky Mountains a couple times and hadn't adjusted the idle recently. For now, i've screwed the idle adjuster all the way in. If i tug on the throttle linkage at the pump, the engine dies. Sure is quiet like this, purrs like a kitten. I'm guessing the idle is around 500 RPMs, maybe lower.

The slow idle should help rock crawling. It sounds much like a Bobcat this way. If i don't let it idle for extended lengths of time to avoid wet stacking, are there any other repercussions i should be leary of? Anyone know what size nut i should use and if i should use a lock washer, or get factory replacement parts from Dodge?
Thanks for all the tips,
Matt