SeaRay Jim

But Tyler may be able to tell you exactly what he did to the programming which might also tell you what was done to the motor since his programming would take that into account. At minimum, he could tel you if he raised idle, and if he did, there was a reason for it.

Dave_N

I am saying that the engine needs to be able to achieve and maintain the programmed Desired Idle Speed, whatever that is.

That said, I looked at some recorded data files I have from similar modified 502 MPI's (Arizona Speed and Marine reprogrammed ECM's) and they had increased the minimum Desired Idle Speed to 750 RPM from the 600 RPM minimum on stock 502's.

So to try answer your original question, if your ECM is programmed for 750 RPM idle speed, there is no way you can reduce the idle speed without sending it in to be reprogrammed.

Dave

mjb

First - you should take Dave N's advice. He knows his stuff!
As Dave said, the ecm program controls the idle speed, NOT the throttle plate set screws....and don't attempt to change the set screws unless you have a scan tool and know how to use it. It is very common to have the idle spped increased when an ecm is reprogrammed, especially when installing a larger cam. If that was done then there is no way to lower the idle speed without reprogramming the ecm.

cloudmaster_321

turns out my computer was not programmed by Tyler, but was reprogrammed for an idle of 775 in gear. So it is doing what it is supposed to. Thanks for the responses though.

foolinjected

were is the iac on a 2001 502

Pat McPherson

It's on the back of the Throttle body. You need to remove the TB to get to it...

Smitty

If you have trim tabs--drop em down at no wake and it will slow you down a little. If you have a cam change it will probably need to idle that high.

foolinjected

thanks pat

Bajajack

my 454 MAG MPI has a Arizona Speed and Marine "program" in the ECM and it idles at 750 rpm, if I advance the static timing 2-3 degees it picks up another 25 rpm. this was checked with my dealers scan tool.

JJS2007

This might be a shot in the dark but you might want to check what setting the tach is on. That can also throw you off a bit. Other than that you can cheat it a bit with the cable. Just a bit though.