Offshoreonly.com - 496HO rough idle

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Quote:

Originally Posted by monstaaa (Post 2640365)

the 496's have an i.a.c muffler located just above the throttle plate in the little square opening. chances are it is shot and never replaced. an easy check is visual but also the hissing noise at idle. check it, pull it out using a small pair of needle nose pliers.
also just becasue the iac shows response electricly doesnt mean its working physically, sometimes they show a percentage change in duty cycle with no physical changes in the actual idle process because the plunger which is the mechanical part of the unit freezes and doesnt alter the idle. a good sign of this is alot of salt on the arrestor. also do the check key on engine off and listen for a hum from the iac.

good luck.

Thanks Monstaaa, I did check the iac muffler. It was a little dirty. I cleaned it the best I could and put it back in. I'll just get a new one. How important is having the muffler there? I noticed that the idle smooths out once the motor gets up to temp.

Quote:

Originally Posted by Dave M (Post 2639586)

P.S. I hope you weren't effected by the quake?

I had just left the hardware store and jumped in my truck. I got bounced around pretty good, but no damage.

As far as the IAC muffler, you don't need one at all. I know Raylar pulls them out of thier engines. Personally, the intake noise is too much for me without the muffler. Just replace the muffler when you do your annual service and your good.

Dirty injectors? I've cleaned mine three times by removing and tapping out a fine grit from each then blasting it clean inside with plastic safe electrical cleaner.

Don't forget to take a reading using a mechanical fuel pressure gage from the shradefr valeve on the fuel rail to ensure your fuel pressure isn't dropping off from a weakening boost pump. Should stay consistently between 38-43 psi.

Another angle (fuel related) friend told me is to check the anti-syphon valve where the fuel line enters the tank.

What is this muffler you guys are refering to???
Anyone able to post a pic??
thanx
mike

Quote:

Originally Posted by verbi69 (Post 2641805)

What is this muffler you guys are refering to???
Anyone able to post a pic??
thanx
mike

It's #5 in this pic. It's basically a little piece of foam.

http://www.mercruiserparts.com/Show_...rottle%2DShift

Thanks Dave, thats what I thought.
I recently discovered that in my 496 while servicing the flame arrestor- I thought it had sucked up something....
-called the dealer and was told it should be there....
Now I know the proper terminology,
thanx,
mike