I finally got my new engine started, and it seems to run fairly well...but the damn thing zooms to 3000 RPM at idle. I checked the engine for vacuum leaks, and set the IAC closed and tried that, still idles high. Double checked for vacuum leaks and loose wires/hoses...I'm stumped. Anybody have any more ideas of what might cause this? I checked everything I could think of. Mods in sig...

Is it possible something electrical could cause it? I just finished building the car up from a bare chassis using a parts car so maybe I forgot a wire or something?

 

have you turned the idle screw down on the throttle body that opens the blades, do you have a stock TB?

 

I have a stock ported TB. It hasn't been tampered with, and ran fine on my car when it was a 350...

 

Make sure your TB is closing all of the way. Take off the elbow and look at the butterflys

 

I checked for binding in the accelerator cable and the TB itself. It comes back to fully closed against the stop screw everytime. I'll pull the bellows off and make sure everything is good, but I'm almost certain it is.

 

Possible tune issue?

 

if i had to guess, probably computer related. (if u have no vacume leaks)
it wont be the throttle body, ur computer controls ur idle.

 

That's one of the things I figured. So I grounded the computer to close the IAC all the way and disconnected it. Then I pulled the jumper and started the engine. Engine went to 2k RPM, but still worked it's way up to 3k, instead of jumping straight up to 3k.

Sounds alot like a large vacuum leak to me. But there are none that I can find. Any possability of an internal leak? I wouldn't think it is likely because everything is new, but you never know.

 

ttt

 

Dave,
I wonder if that PCM might've had another problem with it besides the corrupt flash. If all else fails (trying to find a vacuum leak or another problem causing the high idle) you might want to try a different PCM.

 

I'll do that. I'll check tomorrow. If there was another problem with the PCM, what would it be and would it be fixable?

It seems to run fine otherwise. Maybe we can transfer programs from one PCM to another...?

But one thing confuses me. The reason I grounded the computer and pulled the IAC connector was so the computer had no control over idle speed, while it was closed. That way I'd get the lowest RPM the computer could give me without the computer interfering(raising the idle). But I still had the 3k RPM idle with the IAC closed and unplugged. How else could the computer cause the high idle in that case? Doesn't seem likely to me.

One thing does come to mind. While I had the intake off, underneath the tray on the bottom of it, I noticed a slot cut in the bottom of the intake, through it into the passages where the PCV valve and vacuum fittings are. It looks like it was there from the factory. I had another intake that was from a different place, with the same kind of thing. I have my EGR and AIR blocked off. That wouldn't cause this kind of problem, would it? Dont all LT1 intakes have those?

 

If there was another problem with the PCM (which from what you're saying, it doesn't sound like) then I wouldn't be able to repair it, but yes, we can just transfer the tune to another PCM.

 

dave, hook my pcm up to your car and see what happens.

 

any news on this??? i just cranked mine tonight since almost 6 months and my car zooms to 3K to 3500 rpms on startup...please any help is very much needed now as i want to hear this thing lope!!!!!!!

 

ttt..