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2012 Suzuki DF-115A 'sometimes' stalling when going to and/or from idle...IAC?

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  • 2012 Suzuki DF-115A 'sometimes' stalling when going to and/or from idle...IAC?

    Hi all. Over the last few years I have been dealing with a problem that comes and goes. After reading through many post, I have have a feeling I need a new IAC but I just wanted to run some symptoms by you all to see if that is in fact the case. My Suzuki dealer here is so busy here, they never pick up the phone, they are not taking any new service calls, and when you do get through on the phone, the stress felt of me bothering them cuz they are so busy renders the call useless. OEM IAC valves are also on back order and they said it will be 5 or so months until they get them.


    Every once in a while, the engine will quit as I come off plane and bring the throttle to Idle (in gear). The engine will always start with no problems and idles at around 650-700 RPM. There has been a time when I put the boat in the water, start it up no problem, put it in gear to get to the dock, then it would quit when I put it in neutral...but it started no problem, and throughout that 2 day camping outing it got better. Last night however, after a few hours on the water with no issues, I got to the dock to take the boat out and it died going to idle. Started no problem, but then would die every time I would put it in gear (10 times)....unless i give it gas. I got home and my battery voltage at the battery was 12.7V. I have never had any codes pop up either.

    Edit 1. Today I put the muffs on and started it in the driveway no problem. Idles high at first then slowly works its way to 700 after a minute or so. I put it in gear and it dropped to 600 then back to 700. I think if i was in the water with a load on the prop it would have died. I did that a few times (5) and then it started being able to handle being put in gear without any RPM drop whatsoever. What i did see though is the RPM gauge needle (not engine) slowly wander to 1100 for about 10 seconds. What the heck.

    I have no codes at all.

    Does an IAC either work or not work? Can it start to fail but work sometimes? I found a thread that references 2013 DF115A IAC/ECU issues. Am I experiencing the same thing where it might also mean I need an ECU? I am the second owner so am not sure if warranty would come into play.

    I actually thought I solved the problem a few weeks ago with a new battery after reading in this forum that that may help. I noticed my voltmeter on the boat drop quite a bit (13.8 to 11ish) when approaching idle on the old battery so I thought maybe that voltage drop as i approach idle might have something to do with it. My other battery was old and bad but last night the problem was the worse it has been and that was with a new battery. I will say that when cruizing around my voltage (on the boat voltmeter) is just under 14V. Should it be higher?


    The engine always starts no problem and Idles at around 650-700 RPM. Over the last few years I have replaced the low pressure fuel filter, the spark plugs, I have ran sea foam through a tank of gas, I blew through the gas tank vent and there are no restrictions, i installed a new battery, I took the IAC off to look at it and clean looked spotless and brand new so I did not spray or clean it. I did take a resistance reading and it was 10 ohms...should be between 8 and 12 so it's good. I lubed the neutral switch on the engine.


    1. I do not have a SDS tool and the manual pretty much says to use an SDS tool to test the IAC function and duty cycle. (I am not quite sure what duty cycle means by the way).
    2. I did not physically clean the IAC as it looked spotless. I suppose I should give that a shot. Someone mentioned having to reset the Idle and IAC after taking it apart but it seems you need an SDS tool to do that.
    3. I did not check anti siphon valve that Moonlighter has talked about in the past. Not sure how to.
    4. I did not look at the neutral switch at the throttle quadrant. It is buried behind a carpeted wall. With my symptoms should I do that?
    5. Obvious one, I did not put a new IAC in yet. Sourcing an OEM one is not easy. I think I found one for a Suzuki Aerio on RockAuto. Should I go that route or buy a used one off ebay?

    I'll leave it at this for now. I now this was long but I hope something I said might trigger something obvious even if that is to get a new IAC.

    My wife says to just get a new damn


    Last edited by Crank04; 07-09-2021, 11:06 AM.

  • #2
    You have not mentioned the fuel line primer bulb state when any of this happens. When I had issues with fuel starvation it was when I was throttling up to plane. Primer bulb was tired and needed replacing. No issues with fuel, right?


    • #3
      Briscoe, thanks for your reply. I actually did go to the back of the boat last night when it stalled 4 to 5 times trying to get it in gear and the primer bulb was stiff and full. I have had this issue for a few years now and a good 8 to 10 tanks of gas. I always use low to no ethanol gas and stabilize it in the winter. Boat is always taken out of the water after each use and stored indoors.

      I did take the IAC out today and cleaned it out with some carb cleaner. It looked clean to me with no deposits but flushed it anyways. After putting it back in, I put the muffs on and started it and put it in and out of gear and it didn’t stall. The rpm actually didn’t budge at all. Normally there is a slight fluctuation, to which I assume is the iac doing its thing to accommodate the load.


      • #4
        If in any doubt, I would replace it.

        The risk is that if it fails, the ecu can burn itself out trying to make it work. This is a known issue on the early A series DF115/140 models.


        • #5
          Moonlighter, good info provided on the A series. I was not aware, just as Crank04 wasn't, I'm sure.
          One thing about it Crank04, you had nothing to lose spraying it out. Post back and let us know if it required replacing. A can of sensor spray is so much cheaper than new IAC.


          • #6
            What was happening to some of the A series engines which use the two wire iac valves, were shorting the internal windings and cooking the output driver transistors.
            His is still in spec but it is something to keep an eye on.