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Boat runs rich

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Hi first off this is my first malibu 2002 23lsv, owned mastercraft 205 needed more room. Anyway on first start up this thing runs rich and has low end misfire and mis under acceleration like plugs fouling out. After a few minutes of warm up all is well. I am a mechanic by trade and hold several ase licences and a smog tech and gm tech. Can you hook a scan tool up to this, if so were is the data port located or is this a fix system. I suspect the coolant temp sensor is making it run rich until warm up but i would like to see the data stream of the ecm. any help would be good. I know how the check the cts , tps and all the sensors buy hand i want to see what the computer sees.

thanks dan

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The plug in for the ECM is located on the back of the motor, usually located right by the ECM itself, the plug is going to be unique to the marine industry.

We use a Delphi controller but they are a MEFI version, yours is most likely a MEFI4 controller.

Diacom is the program you need to communicate with our MEFI controllers but be prepared to spend some money. Diacom Marine runs $600+ and you still need to purchase the cable and adapter to your version ECM.

Here is a link to Diacom: http://www.rinda.com/acro/prodlist.pdf

Your suspicions are right, TPS, MAP, ETC sensors can all cause your symptom and most likely one of them is having a issue.

Wish you luck


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A simple ohm reading of the ECT sensor at different engine temperatures will let you know if it is working properly. The values you would want are in any GM emissions service manual.

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