454 mag mpi won't idle
 

I was out this weekend and left the dock and went to the sand bar (everything was all good), went to leave the sand bar and the port side motor wouldn't idle. Decided to go back to the dock, no loss of power it ran fine off of idle and got to the dock and still wouldnt idle. Checked fuel pressure, it was good. Check that the idle screw, it hadn't back out it was good. I could get it to idle at 650 rpm if I bumped the throttle a little, almost like the idle screw had backed out but not the case. Went to fire it up to check one last thing and it idled perfect. Any ideas, iac motor, tps sensor, map sensor, or do I need to clean any of the? Any inpute would be helpfull. Thanks Eric

It could be any of the above but usually the IAC is the culprit--do you hear the "hissing" sound at idle? Have your computer scanned before you start buying parts.

There was a lot more intake noise out of that motor compared to the other one. It was a hissing type noise.

iac stuck wide open. that is hissing noise.

Pull the IAC out and clean it. They get gummed up with carbon/oil. Take it out and wipe the pintle with some carb and choke cleaner. Also wipe out the passage that the IAC sits in. It will be full of gunk as well. That should fix your problem. I would say the IAC got stuck. Once the crude heated up a little it broke free.
Eddie

Thanks for all the help I will clean the iac and then get a spare to have on the boat.