High idle after intake manifold gasket replacement (sbc)

[MaltbyPenn]

Sorry this isn’t 2f but it is installed in a FJ40 😁.

Had an oil leak on the china wall so torn everything down to reseal. After letting it sit 5 days, I decided to try to start it and see if it would still run. It immediately ran up to 2800 rpm. I desperately tried to shut it down quickly. Thinking I didn’t hook up the throttle springs, I checked to throttle body…nope, springs hooked up and butterfly valves were shut. Tried it one more time and repeated the same start. Btw, it hasn’t been starting very strong but this was very strong.


Now for the details:

It’s a sbc, 383 stroker.

I removed the EFI, Holley sniper along with supply and return fuel lines. Removed the dizzy marking cap location but didn’t mark pointer. I believe I got it back to the direction looking down at the oil pump. Unplugged all EFI connections. Drained coolant and removed hosed. Cleaned and scraped all gaskets, installed new gaskets and rtv’d the china walls. Installed and torqued intake manifold. I also changed the EFI gasket from paper thin to 1/4 inch thick Holley gasket.

Of course I believe this has to do with timing but I can’t imagine how I could get to 2800 rpm with zero throttle.

Any ideas?

 

[ceylonfj40nut]

so you have a carb in place if EFI now? Unclear from above. If Carb, did someone mess is idle screw? Check that it timing is good. Otherwise check timing first.

 

[Skreddy]

Did you start the sniper program over like a fresh install? If it had been had learned how to compensate for the vacuum leak it may need to relearn.
I’d be thinking vacuum leak, really advanced timing (but that high I’d think you’d get kickback trying to start it for being too far advanced).
I think first thing I’d check is backing of the throttle set screw to lower curb idle. Make sure it’s just not set high from compensating for vac leak.

 

[B y r o n]

Sounds like you need to reset the ECU and treat it like a new install. Double check all hoses and connections and initial throttle settings. Get it started and set the timing. Let the ECU learn again.

 

[whitey45]

Big vacuum leak! Pcv hose connected?

 

[peesalot]

find the leak, what manifold ?

 

[MaltbyPenn]

ok, found the issue, the sheathing from my throttle cable was no seated in the collar causing tension at zero throttle. After I properly seated it, the rpms dropped to a reasonable level.

Thanks for all the suggestions!