idle RPM and IAC counts are not responding

**mmigacz** · 03-30-2014

The winter is finally starting to lift in Wisconsin. I pumped water into the block of my boat and started messing around with the idle today. Below is brief summary of my setup:

-351W ford engine
-ski centurion, straight inboard boat
-mild cam
-gt40p heads
-1227747 ECM
-fuel pressure 18psi
-5.7L injectors (truck)
-no EGR
-no VSS
-no O2 feedback (running in open loop for now)
-No Knock sensor (esc)
-Manual transmission set-up
-I do have a wideband hooked up
-I do have an emulator

I got the engine to idle pretty good at 1050 RPM. The crazy thing is, the closed loop idle is set at 850 RPM. The other crazy thing is, no matter how much I open the throttle blades (idle adjustment screw), the IAC counts will not come down. They seem to hover around 79 counts. I attached my bin and and a log file. I let the engine idle from the beginning of the log to about 48 seconds.

Any idea's why the idle won't come down or why I can't get the IAC counts to lower?

burn 03-29-14.bin

new 5.xdl

**steveo** · 03-30-2014

Originally Posted by mmigacz

-no VSS
-no O2 feedback (running in open loop for now)

...

I got the engine to idle pretty good at 1050 RPM. The crazy thing is, the closed loop idle is set at 850 RPM.

...

not that i know anything about that ecm, but think about that for a second ...

**mmigacz** · 03-30-2014

Sorry, the part I need advise on is:

It won't idle less than 1050RPM, even though I have it set at 850.

When I say closed loop idle, I mean the IAC is in closed loop, trying to maintain a consistant idle RPM (850 target).

I could be wrong, but I didn't think the target idle RPM needs o2 feedback to be maintained, right?

**jim_in_dorris** · 03-30-2014

Too much airflow past the throttle blades, screw the stop in and watch the idle.

**EagleMark** · 03-30-2014

How many IAC counts when this is happening?

Yes, Desired Idle in $42 is CL and fully warmed up. Most boats run a low thermastat and never reach what a stock bin thinks is warmed up.

EDIT: Data log shows 160*f, it's not warmed up. IAC counts are in 80's and keeping idle high because it's cold. I'll look at your bin in the AM and see if I can make the changes needed to be warmed up at 160*f and lower your IAC count for cold...