M1009 High idle in park???

[kennedy762]

My 1986 M1009 has been running like a champ ever since I got her last winter. The only thing that still baffles me is when she's been running for a while, the engine seems like it's in high idle when it's in park and neutral. The high idle stops immediately when it goes into any other gear. It's pretty serious, the thing sounds like it's gonna blow!!!
I'm a USMC Wrecker operator, so I can usually figure most things out on my own, but I'm lost in the sauce on this and I need some higher echelon expertise.
Semper Fi

 

[doghead]

Uncontrollable idle could be an indicator of a bad flex ring(not sure what the correct term is) in the IP. You may need to have your IP rebuilt.

Maybe somebody here that has rebuild experience, can offer a better guess.

 

[armytruck63]

Another possibility is a slight air leak in the fuel system, not enough to stall the engine.

I had a crack develop in the fuel hose between the frame and the lift pump. I got a sudden burst of power and high RPM while driving down the freeway, followed by no power and limping to the shoulder.

 

[boomer]

One of mine did that. The collector who I got it from, told me, it was because it always wanted to go, go ,go! He ended up fixing it for me. Then he got another toy, and I traded it back to him.