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IAC valve-gctid407168

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    #1

    IAC valve-gctid407168

    Ruined my perfect day yesterday. Coming back to the dock I always cut in, wife jumps out with bow line and I hit reverse and swing the back in. This time motor died and I hit the dock and than cement seawall in front of dock. Just damn glad wife did not get hurt. Wind was from the stern and the boat just kept going forward. At least bottom did not hit the ramp. My first scrape in 8 years, time to brush up on gel coat repair. Anyway boat will not idle but runs fine at fast idle. Got on line and several talked about the IAC valve will effect idle and I also had a two beep alarm per minute. I crossed referenced the mercruiser part number over to an automotive valve AC423. Picked one up at auto zone for 1/4 price of mercruiser and that was the problem. So far on the muffs it is running fine at idle with no more double beep per minute. Certainly hope that was it and not something else that will come back. Usually the ramp is busy buy it was empty so I just came right in. Learned one lesson, I will always check idle before before moving in to dock. I was only about 800-900 RPM with a cross wind and the 289 just kept going.

    Rock
    Tags: None
    #2
    I feel your pain! I had the same thing happen last year. http://www.baylinerownersclub.org/fo...-hard-starting

    Great idea on getting the iac at autozone, I spent a little over 100 for the mercruiser part. I wonder what the difference is between the 2 and if it is safe for marine application? It's one of those parts that would be nice to have a replacement on board if needed.

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      #3
      Scott,

      Their is one thing thing different. The inside piston shaft has a spring that looks like it will keep it in the open position if the solenoid fails. The old valve was closed when I removed it and cannot even pry it open. The new valve is in the open position. The merc p/n is 862998 which crosses to an AC423 and autozone crosses that over to a TV278. The AC423 might look identical but the TV278 looks designed better with the spring. At $55 you can afford a spare. I only ran it up to 1800 rpm on the muffs but it idles great and checked it 10 times during the day. What I have read is it opens to allow air flow at idle since the throttle body is pretty much closed. See what happens at wide open throttle next time out when I go diving.

      Rock

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        #4
        As the crusty old Scottish Chief Engineer once said, in a brogue so thick you could cut it, "Never approach a dock at a speed greater than you are prepared to hit it".

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          #5
          IAC crap, tell me about it. My Friends were on their way up to meet us in the Thousand Islands last week when their IAC valve failed. Bottom line he was stuck 5 days at a marina waiting for parts. Happened to another boating buddy of mine 2 years ago although his only had symptoms of poor idling and was still able to operate. I tried locating the part for my friend at a large Merc dealer in Alex Bay, NY while he was broken down only to be told. Oh my, we have none left as we changed at least 6-7 of those in the last 3 weeks. This alone made me buy one on ebay to have on board as a spare which should be waiting for me when I get back home.
          Cheers, Hans
          2007 Carver 41 CMY
          Twin Volvo D6-370
          Montreal, Canada
          Midnight Sun I Photos

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            #6
            I think the idle speed depends on what position (how far open or closed) they fail in that effects idle speed. When I get a chance I am gonna cut the old one open and see why it is frozen shut.

            If it happens again I will pull the two hoses off and connect them together to have at least idle speed at close quarters. I got about 8 years from mine and you can only take so many spare parts. Say what you want but is was so easy to work on stuff yourself when it was back before electronic ignition and fuel injection. Now it is like a car, you have to go in to get the codes read and wait weeks for that. Who ever opens a boat dealership and runs it like a car lot will make gold. Could you imagine brining your car in and it sits for weeks before it is even looked at!!!!!!!!!.

            That god for google search!!!!

            Rock

            Comment

              #7
              Mine also failed a few years ago. Maybe it is one of those items that need to be replaced on a proactive basis?

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                #8
                Rock,

                I'm not familiar with the Merc idle air control valve, but if it is remote, that is inlet air and outlet air fittings, it should be relatively easy to remove the valve and install a temporary manual valve.

                On a speed density EFI system, which I believe is what you have, the idle air control valve just introduces a secondary air supply to the engine. When the throttle plates are closed, idle speed can be increased by introducing this secondary supply. It's just a controlled vacuum leak really. Unlike a carburettor equipped engine this "vacuum leak" just increases the intake manifold pressure, which adds more air. The ECM doesn't know or care where this air comes from, it just adds fuel to suit, and the result is an increase in engine speed. If you replace the IAC valve with a manual ball valve, or something similar, you now have a manual idle speed control. Just another hand throttle with a limited range of speed.

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                  #9
                  That is exactly how it works. If it fails again I will pull the hoses and have at least idle speed to return to close quarters.

                  Rock

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