What are the symptoms of a bad IAC?

TurtleTone said:
I was led to believe that they generally last 2-4 years. one that went last year was original which meant it was 5 years old. the other one that went had already been replaced 3 years ago.
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I wonder if it's the salt atmosphere on boats that make them wear out fast? I've had fuel injected vehicles from the late 80's and they were on their original IAC valve. That's almost 20 years! I don't know if mercruiser recommends cleaning on a scheduled plan, but I think that might be something to add for your FI guys.

Doug
 
Vince_nj1 said:
My boat is a 2006 with 6.2 Horizons which I believe are fuel injected. The last time I was on my boat I tried to start the engines without touching the throttles and they struggled to get get started. I featherd the throttles, got them started and then went back to idle and they stalled. I restarted them, got the RPMs up to around 1200 for about 30 seconds and then went back to idle and they stayed running.

Is this normal for a fuel injected engine? Could I be having AIC issues? They run fine when warm, but I find it was odd that they needed a little help to start and stay running when cold.
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what are the chances both would be going bad at the same time? Plus whether warm or cold they would normally still stall. I'd be thinking something else.
 
douglee25 said:
I wonder if it's the salt atmosphere on boats that make them wear out fast? I've had fuel injected vehicles from the late 80's and they were on their original IAC valve. That's almost 20 years! I don't know if mercruiser recommends cleaning on a scheduled plan, but I think that might be something to add for your FI guys.

Doug
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Doug,

You are absolutely right about the GM auto IACs. I've had the same experience. I don't know if the Mercruiser part is the same as the GM part, but it brings up a question - I've used a can of Chemtool B-12 added to my cars' fuel tanks each oil change. Is anyone adding injector cleaner to their Mercruiser MPI's?
 
vince nj1 wrote ... My boat is a 2006 with 6.2 Horizons which I believe are fuel injected. The last time I was on my boat I tried to start the engines without touching the throttles and they struggled to get get started. I featherd the throttles, got them started and then went back to idle and they stalled. I restarted them, got the RPMs up to around 1200 for about 30 seconds and then went back to idle and they stayed running.

Is this normal for a fuel injected engine? Could I be having AIC issues? They run fine when warm, but I find it was odd that they needed a little help to start and stay running when cold.

We have 6.2s also & your description is typical of our winter initial start procedure, air temp < 45º, both engines. No problem in the summer. We did have an IAC failure last summer, engine died when throddle closed.
 
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I'm assuming DTS has no effect, one way or another, on this?

This is another of those things I simply scratch my head and say "why" on. For this to be so common people carry spares I mean. I cannot imagine carrying spare parts around in any of my cars. Harsh environment or not, I think of what my boat cost versus my most expensive car (Jaguar) that has never been near a repair shop.

Thanks for listening!
 
HI any chance they are more likely to fail if engine is using oil? Any truth to that statement?
Thanks
 
There is also one more issue you can have, on my 2003 280 Sundancer with 496 Mag it fouled all the plugs when it failed and we has to replace all the plugs when we changed the valve. Then the mechanic forgot to flash the computer and the. Oat ran like crap. One more trip down to the dock lap top in hand and presto changeo all good.
 
Standard Motor Products AC423 Idle Air Control Valve is the nonn- Mercury IAC part and is $43.00 on Amazon. I carry a spare and correct allen wrench size.
 
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