Well I had turn my idle up the other day because I think my ve is gettin tired and when it gets hot its starts to idle lower. So I turned it up and now when its cold it idles at about 850-900 rpm but idles normal when warm. I came home the other day and decided to rev it up slowly in park and see if it'd take off just like it did before. I brought it up to 1000-1050 rpm and held it there for a while and after about a minute it started to very slowly go up in rpm and I could hear it but my foot hadn't moved a bit. As soon as it hits 1200 rpm it just jumps right up on its own til you let off. I decided to hold it for a second in the same spot to see what it did and it climbed up on its own to about 3000 rpm and then I let off and it hung there for probably a few seconds and I panicked! I got the chill down my spine but then it came back down to an idle. What i don't get though is it will only do this in neutral and not while driving. This 4200 spring is touchy and it does take off after 1200 while driving but doesn't act like it trys to hang or runaway at higher rpms but I guess I haven't really taken it past 3000 while driving yet...this just made me curious and i'm kinda worried about it in the back of my mind. I think I will be investing in an air shut off soon. But what would cause it to do it in neutral but not driving? Just a load on the motor?

 

Thats spooky. Have you tried turnin down the full power screw a little bit and see if it still hangs? Just a thought.

 

There's an extra load of the entire truck and drivetrain on the engine, which is why it's a lot worse in neutral. I had mine do that in a Chevron parking lot a few hundred miles from home after I decided to fiddle with the full power screw. It hung at about 3,300rpm, and didn't come back down....I had to turn off the key, which shut it off. At speed, it would do about 70mph in gear, just like cruise control, and if I put it in neutral it would take off. Learned to never mess with that kind of stuff so far from home. Turned it back 1/4 turn and it was fine.

 

I haven't touched the full power screw for about 2 years or more so I've figured if its gone this long without total runaway then it should be fine. I turned it up once then turned it up some more and It ran dang good so I left it since and didn't dare go more. Plus the head is pretty buggered up now. It did this same thing with the 3200 governor spring but I never got it to hang like that, but I guess I never really tried. I haven't actually opened the truck up for a very long time, haven't raced or dynoed or anything, I've kept it under 3000 rpm, under 30 lbs of boost and under 1100 degrees for a long time. I need studs and springs til I open er up and I think I better invest in an air shut off too before I do open it up to be safe.

It goes down the road pretty good once you get up to speed. Its weird, if I go past my speed a little bit and come back down to it then it cruises a lot better on the flats with lower boost, rpm and egts. So say if i get it up to 70 and come back down to 65 it goes better than just going to 65 mph, but I'm wondering if that is from the torque converter.