Hi guys, I recently added an intercooler to my 540 and bumped the boost from 3 to 7psi. Should be around 850hp now,,used to be 700hp. My idle speed used to sit right at 1100rpm and drop to 850rpm in gear. Motor would never die at idle. After the upgrade, the motor now lopes between 500rpm and 1100rpm and when I shift into gear it dies out often at idle (cold) speed. I had the EFI brain box reprogrammed by the engine manufacturer for the upgrade and everything should be running the same as prior to the upgrade. I have been told there may be a problem with my IAC valve. Where is this part typically located on a motor with Blower shop supercharger and EFI tech throttle bodies? How do I know if this IAC valve is not working right. I replaced the fule regulator and the fuel pressure is 20psi at idle per manufacturer specs. Any help would be greatly appreciated....thanks..
Marc
IAc should be on the t-body itself. If it isnt working at all you can test by unplugging it. If you unplug it and nothing changes then its probably no good. You can pull it out to see if it moves back and forth with the engine running(if it will without it) just cover the hole.
Dan
Thanks alot Dan,,,I will try what you suggest if I can just find this damn thing on here..
Idle mixture will need to be richer with the intercooler. The air is colder, and there is more internal area to cover with fuel. TIMINATOR
Is it tbi ? If it is and you are running water thru innercooler at idle this could cause fuel puddling and your issues. Most will use transom mount pick up's for carb/tbi or a water psi regulator that will let water go to intercooler at certain psi.
If the engine used to idle at 1100 out of gear and 850 in, the IAC never worked. Programmed idle speed is maintained +/- 100-150 rpm depending on how well it's tuned. The lope is a product of the intake pressure signal. Bigger the cam the harder it is to maintain a constant signal. Should do better with a load on it so the idle speed should be +/- 25-50 rpm in gear. Both numbers should cycle around the programmed rpm or the IAC is not working/connected. With no IAC less timing at idle will allow the engine to run in or out of ger better.
Idle mixture will need to be richer with the intercooler. The air is colder, and there is more internal area to cover with fuel. TIMINATOR
Seems like it is running rich at idle now though. Idle fuel pressure is set to 20psi per Keith Eickerts recommendation. Just seems like it is not getting the correct air/fuel ratio at idle and that is causing the loping. Might have to do with the fuel mapping of the EFI box.
Is it tbi ? If it is and you are running water thru innercooler at idle this could cause fuel puddling and your issues. Most will use transom mount pick up's for carb/tbi or a water psi regulator that will let water go to intercooler at certain psi.
It is TBI with offshore pick up for intercooler only. No water in intercooler at idle....thanks
If the engine used to idle at 1100 out of gear and 850 in, the IAC never worked. Programmed idle speed is maintained +/- 100-150 rpm depending on how well it's tuned. The lope is a product of the intake pressure signal. Bigger the cam the harder it is to maintain a constant signal. Should do better with a load on it so the idle speed should be +/- 25-50 rpm in gear. Both numbers should cycle around the programmed rpm or the IAC is not working/connected. With no IAC less timing at idle will allow the engine to run in or out of ger better.
Thanks for the info. It definetly idled at 1100 in neutral and 850 in gear. Smooth, nver stalled even when cold start. The cam was not changed. The only thing we did was add intercooler and bump the boost from 3 to 7. I also had the EFI box reprogrammed by the engine builder to match the engine upgrade which is exactly the way he does it at his shop. It does better when the engine is hot but still has the big lope. Eickert says it should basically idle the same as it used to at 1100/850 (gear). Here is a pic of the motor before the adding the intercooler. Where is the IAC plug in on here if you can direct me please. Thanks for the help...
Cool on the intercooler water set-up.
IAC will typ have 4 wires going to it. They will usually be screwed to t-body with 2 screws.
Did we pull the distributor or adjust the timing by chance ? If the initial timing is off this can really make a SC EFI motor idle like poop. Most EFI systems have their own peculiar set of steps you have to do to set the initial timing. If not followed 100% then the timing won't be where you think it is. Must check with Eickert (sp?) on how exactly this is done.
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