Surging Idle - 490 HO

[SunDeckTodd]

Afternoon - my mechanic just put a rebuilt 496 HO in my 2008 Sea Ray. Worked through a few bugs, sent the ECU off to get tested (tested good). At this point, the boat fires right up, no errors on the scanner, but once warmed up it wants to idle down and die. Otherwise cold and if you give it throttle, it's happy.

Any thoughts on what could be the issue to track down? I'm going to put some new fuel in it, but doubt that's an issue since it idles fine cold and above idle throttle. A few folks suggested IAC or the throttle body mufflers, but he said it doesn't have an IAC (could still be the mufflers I suppose). Not sure if this is due to SmartCraft possibly as to why it doesn't have an IAC?

He suggested a Merc AD hook it up to diagnose and will probably end up going that route, but figured I'd bounce the question out here to see if anyone may have some ideas I can try before submitting to a Merc dealer.

Thanks

 

[Jimmy Buoy]

I believe all 496's are the same (I had 2 8.1S engines which are the same but for inboard applications) and they sure do have an IAC.

It's on the back of the engine on the intake. Follow the small black tube from your throttle body back and it is attached to the IAC. Easy to replace and GM parts will work just fine for much less.

 

[techmitch]

Afternoon - my mechanic just put a rebuilt 496 HO in my 2008 Sea Ray. Worked through a few bugs, sent the ECU off to get tested (tested good). At this point, the boat fires right up, no errors on the scanner, but once warmed up it wants to idle down and die. Otherwise cold and if you give it throttle, it's happy.

Any thoughts on what could be the issue to track down? I'm going to put some new fuel in it, but doubt that's an issue since it idles fine cold and above idle throttle. A few folks suggested IAC or the throttle body mufflers, but he said it doesn't have an IAC (could still be the mufflers I suppose). Not sure if this is due to SmartCraft possibly as to why it doesn't have an IAC?

He suggested a Merc AD hook it up to diagnose and will probably end up going that route, but figured I'd bounce the question out here to see if anyone may have some ideas I can try before submitting to a Merc dealer.

Thanks

If your mechanic say's it doesn't have an IAC, I think it's in your best interest that you don't ever let him work on your boat again.