I would call mercruiser techs. 405-743-6566

Has it done this since the ECM was reprogrammed? Was is not makng sense is that the IAC motor is able to close when reset (at key off) but not able to close when the engine is running. Possible programming issue?

Dave

That's exactly correct. I had the ECM reprogrammed while the motor was being built. I never had this problem until the new motor was installed with the reprogrammed ECM. So you're thinking possibly a problem with the ECM?

Well I was thinking open circuit or bad IAC motor, but the more I thought about it, the more I thought it does not make sense. An open circuit or bad IAC would just stay open all the time. It would not close at key off (reset) like yours is appearently doing. So, it seems like it's working, but just not getting any signal to close from the ECM during operation. I would put in a call to the programmer.

You could confirm the IAC signal (or lack thereof) if you wanted to. There are inexpensive IAC testers available. They just consist of two or four LED lights that flash when the ECM is sending a signal. You just unplug the IAC and plug the tester into the connector.

Dave

I just got off the phone with Jim from Arizona Speed (the guy that programmed the ECU). Jim is thinking the throttle position senser needs to be adjusted. I asked him how to do this but he recommended that unless I'm familiar with it and have the proper tools I take it to a Merc dealer. Unless someone here feels differently I'll probably call around and look for someone in my area to take a look at it. Hate to drop it off this time of year though, no telling when I'll get it back. I'm sure everybody is flooded with work right now.