I had this happen on mine...ended up being the throttle cable was a little tight causing the idle to be high. The ecu attempted to bring down idle by pulling timing. 6* of timing and my manifolds were glowing.

 

Hadn't thought about that one, but sure can see it happening if the base idle spark advance was low enough and the idle over speed table had high enough numbers in it. Both mistakes inho.

 

Base idle set to 18, other table stock to the best of my knowledge. Most idle tables I left stock. I had a "base tune" sent to me that I have been moving back to stock. I will have to go back and look now though when I get off work, lol.

 

Ok I will pull the throttle body off and make sure the blade is shut completely. 90mm edelbrock unit.

Now, the blade has a hole drilled in it from the previous owner, and I should have had it fixed before the dyno but slipped my mind so I know, I know.

Question is, if it was dyno tuned with that hole, shouldn't idle know that and be fine?

 

Don't pull it off, just check to see what idle it is commanding and what it is actually idling at (according to the computer, not your yach).

 

Is this something you can see via the scan I posted?

 

Not on my phone

 

Apologies, meant you as in myself, not sure on this spectrum of car stuff

 

Yup, look at target idle speed in the tune for a specific coolant temp and see where your car is idling. If it is targeting 800 and you are idling at 1100 rpms then you may have to adjust the throttle stop or cable.

 

Just went back and looked and compared my file to a stock 2000 z28 and it is identical in the over speed table.

 

Looking through this scan, and I can find what the PCM is seeing rpm wise but how do I compare that to what it wants?

 

You need to log commanded idle RPM as well as actual RPM.

 

Or just look in the tune at the idle target portion of the tune if you have that ability....do you have a copy of your tune you can open and look at?

 

Most scan tools list it as Desired Idle. If the actual RPM is higher than Desired Idle, there could be your problem.

 

Well game plan is to fix the stupid hole in the blade then check for vac leaks

 

Mine, brand new Nick Williams has a hole, that is not uncommon.

 

If it is idling higher than the Desired RPM, simply try closing the throttle blade.

 

Throttle blade is shut when at idle, going to adjust the blade within the bore so it doesn't stick.

 

There's nothing says you have to keep overspeed spark
correction. You might keep underspeed, where it stops
the motor dying, but let idle air trims try and deal with
the high side by themself (if able). Don't see any info on
what IAC position is (if cable throttle), whether it has
or hasn't got authority - that is the question as regards
vacuum leaks and hole sizes.

 

When he says shut he means adjust it more. check you IAC's and report to us the numbers your getting. That will tell you a little right there. But as said above timing will cause that problem