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2009 DF70a will not idle, changed IAC...

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  • 2009 DF70a will not idle, changed IAC...


    2009 df70a Will not idle, could start motor by adding throttle, and it will run 2k-5k+

    Changed iac valve: seemed to idle better, took boat out after warm up. it dies doing under 2krpm and stalls, harder time starting now, but still can with throttle to get back to ramp.

    computer reads:
    403 hours
    ​​​​​​failure at 395

    no. CMP sensor fail 3 times
    no. CKP sensor fail 2 times
    no. Low Oil pressure 33 times
    no. over revolution 4 times
    no. overheat (temp) 1 times
    no overheat (gradient) 6 times
    caution system name (3) overheat grad.
    ignition timing BTDC 5
    iac valve duty 65%

    compression tested all 4 cylinders 2 weeks before failure while buying motor, 150psi on all 4 cylinders.

    replaced fuel filter, drained vst tank, replaced fuel water separator, added startron fuel stabilizer, changed iac. changed spark plugs, changed oil in lower unit and engine, both very clean.

    any advice? trying to not just keep throwing parts at it if someone has had this simular issue! im stumped!

  • #2
    Have you reset the Idle, get your hands on a service manual and follow the Idle procedure or search this forum on the subject


    • #3
      S e l f f i x e r dot c o m(all one word) has a service manual for your engine in pdf form. I have a 2009 DF90A, same engine series as eastbeaster. There is no idle adjustment. The manual states for Unstable idling/trolling or engine tends to stall possible causes Shift position sensor failure, Throttle position failure, IAC control system failure, IAC passage clogged, ECM failure, Wire continuity/connecttion failure, Fuel injector(s) clogged, Fuel pressure regulator failure, High pressure fuel pump failure, Fuel filter clogged, clogging, bending or improper routing of fuel hose. The genuine Suzuki service manual mentioned above has all the test procedures for the causes listed.


      • #4
        My post is waiting for approval from the ***** group. There is no idle adjustment for that engine, the idle is determined by a host of sensors. When you changed the IAC valve did you check the passageway for clogging. My next post if allowed I’ll try posting a service manual in pdf form thats for your engine.


        • #5
          S e l f f i x e r d o t c o m (all one word) has a genuine Suzuki service manual. The manual has all the test procedures for the sensors that the ECM reads to determine the idle


          • #6
            I have a newer/smaller motor, so no direct comparison. But I notice in your error list a lot of oil pressure & temperature errors. I would certainly be concerned about the oil pressure... But I just wanted to point out that when the impeller in my motor started wearing out, the first symptom I saw was that I'd get temp alarms when the engine was idling. The motor would overheat at idle because the broken impeller wasn't generating enough water pressure at low speed to cool the motor. I can imagine the same may be true re: oil pressure. When my motor overheats, an audible alarm sounds, and the ECM limits the motor to run only at low RPM. I found that if I ran the engine above idle speed, the temp would come down and the motor would run well. But at idle I would get a temp alarm. This probably doesn't explain what you're seeing, but something to consider. Does your motor sound an alarm when the temperature errors occur?


            • #7
              UPDATE: 2009 DF70A

              -Replaced entire fuel system, lines, filters, water separator, high pressure pump/ fuel regulator, cleaned VST tank.
              - New IAC valve, old was confirmed bad by dealer.
              - cleaned all electric contacts/ added a buss bar and new fuses.

              -* motor now starts, idles high at 1,100rpms. normally it was around 650rpms, does not go into gear at all, motor surges when you try.

              - * suzuki alarm 3-3 code goes off I replaced neutral switch under shift actuator under cowling and same issue.

              -ohmed out the "White wire" tested good from motor to battery, then also ohmed from harness connector in motor to one inside center console was good. cleaned up contacts with a stainless pick and put back together.

              - took out ecu to look at connections, all looked great.

              - my problems point to a harness or ecu failure itself. considering my origional problem I could rev engine and it would run even do 30+mph no issue, but not idle. im confused

              Seems my issue has reversed and im not any closer to finding a solution. 33920-87L50 is my ecu they retail for over $1,800. i feel like this really isnt my issue, but it is very expensive.

              any suggestions??? ive already lost half my boat season


              • #8
                There is an idle reset procedure that has to be done after changing the IAC valve if I am not mistaken


                • #9
                  Originally posted by ECU1984 View Post
                  There is an idle reset procedure that has to be done after changing the IAC valve if I am not mistaken
                  I have a 2009 DF90A(same engine family) and there is no idle adjustment. As per my service manual idle is controlled by the ECU based on input from sensors.


                  • #10

                    For DF90 idle adjustment , I have done this several times on my DF140 after IAC changed out.
                    Follow the procedure outlined at the bottom for changing the IAC duty cycle, set to proper rpm
                    It allows you 5 mins to change idle speed.


                    • #11
                      Links too blurry for me to read. Can you try something else, I’m really interested in reading that, especially since there is nothing in the Suzuki service manual. That being said the 140 is a different family of engines, my service manual is 2009 DF70A to the 90A


                      • #12
                        From DF-90 Suzuki Service Manual
                        The DF90, Df100, DF115 and DF140 are the same "family"
                        The "air screw" is sometimes behind a black rubber plug on the throttle body.
                        The below is to be done after replacing IAC valve. This is the reset procedure

                        Product Details
                        This is the original Suzuki service manual not an incomplete after-market manual you find at your local marine supply store. Perfect for all maintenance tasks and rebuilds. Includes all specifications as well as step by step service procedures.
                        For the following models:
                        • DF 90 All Model Years
                        • DF 100 All Model Years
                        • DF 115 All Model Years
                        • DF 140 All Model Years

                        ADJUSTMENT :
                        If idle speed is out of specification, perform following adjust-
                        ment procedure.
                        4. Check that CTP switch is in ON position.
                        5. To set the IAC valve duty to constant 15%, raise engine
                        speed to 1000 r/min. or higher by turning the by-pass air
                        screw and hold that speed for 10 seconds.
                        At this time, caution buzzer will sound to notify that IAC duty
                        is in fixed mode.
                        Turning air screw counterclockwise :
                        Turning air screw clockwise :
                        • While IAC valve duty is at fixed 15%, caution buzzer will sound
                        for repeated 0.5 second with an interval of 3 seconds.
                        • The 15% fixed mode of IAC valve duty will continue for 5
                        minutes and then it will be automatically cancelled.
                        6. During fixed mode of IAC valve duty, adjust engine speed
                        to 625 25 r/min. by turning by-pass air screw
                        Last edited by ECU1984; 07-04-2022, 01:16 AM.


                        • #13
                          Many Thanks. I do not have any of the above procedure listed in my service manual. Suzuki made some changes for the 2009 model year. I believe 2009 was the first year that the “A” series engines where introduced and part of the changes was the 90 hp (2009 and up) was reclassified in with the 70,80 and 90HP family. I’ll be interested to know how it goes with eastbeaster with his IAC adjustment procedure.


                          • #14

                            ​​​My idle stuck on high was due to corrosion ruining my throttle body adjustment screw. I changed the throttle body, got motor to start and return to its origional issue.

                            3-3 code neutral safety switch code.
                            motor starts, idles then dies
                            can rev motor up in neutral to keep running, but when you stop adding throttle it sputters and dies.

                            neutral safety switch is good, replaced anyway.
                            battery voltage is 12.6v
                            voltage between neutral safety switch wires unplugged when ignition switch is on is 11.5v. not sure if this qualifies as a drop or if this is normal.

                            I have heard issues of shift actuators causing neutral safety issues and also ECM, or wire harnesses. the main harness has been ohmed out and tests good also connections cleaned all the way to ECM.

                            any other tests i can try before buying an ECM? Im chasing my tail around.