IAC Valve - Carbon Build Up

[Brew2]

2004 5.0 Mercruiser MPI

Engine was surging/stalling at idle last fall (after a long run at idle towing someone in). After winterizing, I took off the IAC Valve and discovered the hole in the bottom of it was totally blocked by carbon. Cleaned it up and reinstalled, but didn't start the engine again because I had just finished winterizing.

Started the motor for the first time this weekend and it seems the surging is not as severe, but still happening.

My question is....would carbon build up within whatever is on either side of the valve? Assuming yes, is there a way to clean it or am I just going to have to keep removing the valve every so often to clean it up and eventually get rid of the carbon?

Also, would it make sense that my long run (30-45 min) at idle would have caused the carbon build up in the first place?

Thanks.

 

[Brew2]

Re: IAC Valve - Carbon Build Up

^^^

 

[JustJason]

Re: IAC Valve - Carbon Build Up

Are you sure it was carbon and not just a crudded up piece of foam known as a IAC valve silencer?

 

[Brew2]

Re: IAC Valve - Carbon Build Up

Nope....was definitely black sooty carbon of some sort. Used an old tooth brush and some dish detergent to clean up the valve opening. Stuff turned my hands black.

 

[Brew2]

Re: IAC Valve - Carbon Build Up

^^^

 

[Brew2]

Re: IAC Valve - Carbon Build Up

Any other thoughts on cleaning the carbon out or how it might have came to be in the idle air intake system??

Thanks.

 

[Brew2]

Re: IAC Valve - Carbon Build Up

Problem solved.

Turns out that there is an air filter of sorts at the end of the hose that runs from the IAC valve to the throttle body. Manual calls it an "IAC Muffler". You access it via the throttle body. Basically is an inch square piece of foam like material.

Mine was totalled clogged with carbon. Cleaned it up and just reinstalled until I can get to a dealership for a new one. Solved the idle surge problem immediately.

 

[JustJason]

Re: IAC Valve - Carbon Build Up

That's what I was refering to when I said Iac Silencer... either way, glad you found it!