Skull Leader

After a good year of not driving Skull-1 around due to a loose pinion nut (figure that one out) and a few other issues, I test drove it for about a mile or so with no problems. Everything was fine until I couldn't stop like the throttle was stuck open. Coasted to a stop, then turned the key off while still in drive.

Put it back in park and restarted, RPMs jumped up to 3000+, kept revving by itself. So I popped the hood, throttle cables are not stuck, no other signs of breakage. Pushed Skull-1 back home then tried ignition again. RPMs jumped up to 5000. I'm guessing the transmission gave out somehow and the engine is spinning without resistance.

I'm gonna look underneath when I have a chance. I'm just kind of right now.

A4 transmission behind an LT1 in case you forgot.

Injuneer

The engine can't redline without air. It idles all the time at spec (550rpm in gear/650rpm in neutral) with no/minimal resistance from the transmission. Take the inlet elbow off and verify that the blades are fully closed.

Skull Leader

Hmm, I hadn't thought of that. You think the throttle blades are stuck? I would take a look but Skull-1 is at my sister's house.

Injuneer

I bent the blades with a nitrous burb in the intake coming out of a burnout and it idled real high.

BlackLT1_Z28

Not a pro but you could be experiencing a high revving engine at idle due to a vacuum leak. I think that would be an extreme case. I had the throttle blade stick on a fast 90 on a manual ls1 car while driving and had a similar problem.

Skull Leader

Welp, I checked all the hoses on the intake manifold and could not find a vacuum leak anywhere. Took off the intake tubing also, throttle is fine and butterflies seal tight. I just can't figure this one out? Anymore ideas?

Injuneer

Since this does not appear to be a "Drivetrain" problem, let's move this to LT1 Based Engine Tech.

Did you check the throttle body gaskets, including the one on the bottom for the IAC controller?

slick1hunting

Disconnect the cruise control on the throttle linkage had my cruise malfunction and had similar symptoms. Freaky as heck car wanting to be at 65 while in town and on startup after having to kill the motor.

andysc

look closely at the bottom of the rubber elbow that attaches to the throttle body. Mine tore and was hanging the throttle blades wide open. Was racing a
AMG and was just getting ready to pass him when this happened. Kept bouncing off the rev limiter. I bet this is your problem. My solution was going to a ls1 lid.

hth
andy schuck