350mpi black smoke rough idle

[cappie]

I have twin 5.7 350mpi's. Changed starboard long block last march and noticed by the end of the season that during cold starts, black smoke coming out of the exhaust. Yesterday I started for the first time this year and it looks like it got worse. It also is running a little rougher than usual making noise at low rpms. The only other issue with this motor is the sea water pump is bad and I am getting new kits today to fix that.
I have the merc scan tool and will hook it up this weekend but thought some of you might have some ideas.
Thanks
Erik

 

[bomar76]

Re: 350mpi black smoke rough idle

Sounds like it's rich as hell......injector(s) stuck open?

 

[cappie]

Re: 350mpi black smoke rough idle

Ordered a new IAC sensor today as I was told if it went bad the scan tool would not pick up a code for it?

 

[bomar76]

Re: 350mpi black smoke rough idle

IAC's are easy to clean.....remove, spray the hell out of them with carb cleaner, scrub with a soft wire brush and reinstall.