I am programming Eprom chips myself,,, 165 ECM,,,6E mask. Please check sig below for engine details.

My problem is stalling when I do a warm startup. The engine will suddenly drop in RPMs, go straight down to under 500RPM and the engine stalls. It seems that the IAC is not keeping up.

Tonite, I had my scanner going and the IAC steps was 0 when the stall occurs. I do not have the Eprom setup for 0 steps, how is this happening. However, The IAC does work with step count going very high when I punch the throotle.

When I do a cold startup, the IAC step count is high and as the engine warms up, the counts reduce allowing the RPM to slowly fall, all is good here.

The constants table has several IAC related items and there is the "Warm IAC Park steps VS coolant temp." table. what should I work with?

For example, there are three Stall Saver spark Enable constants, mine are set at 200, 200, and 300RPM, respectively. How do these constants work, what do they do for me?

 

first things first.

1) what's your IAC step count at a fully warmed up, unloaded (all electrical/mechanical loads turned off) idle? Stock some of these vehicles have step counts at 60+ at a warm unloaded idle, and it can cause all sorts of dumb issues. suggest that you get below 15 or so on the IAC steps at a warm unloaded idle.

Is the dying actually caused by the IAC steps? In otherwords, do you see the IAC steps at 30+ or higher, and they suddenly go to 0 which _results_ in a stall? or are they already near/at 0, and it stalls out of the blue for some other reason?

 

I'm at work now so I dont have may Eprom file here to check. But, I think that the IAC step position vs coolant table has 20 IAC counts at 60 or 80C, and 15 counts for 100C & above. Last evening, my AutoXray showed 0 counts for the IAC during my stalling episode. I had to punch the throotle to keep it from stalling, but it still stalled out at least twice on me. And the park position count for the IAC is 15 or 20, so I do not understand why the IAC count would ever be 0.

Maybe its a warm start problem while I am in open loop, because after a few minutes the engine will idle just fine, if I have driven it a few miles on the street.

 

Wouldn't a vacuum leak force an unwanted 0-step IAC count at idle? And on a MAF car, that's air the ECM hasn't accounted for, which means you're running lean (particularly when warmed up). At cold the ECM is already throwing extra fuel into the system, so it likely masks the problem.

Just my

 

Sounds good, I will tighten the Sr bolts up and look for an vacuum leak.