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Mmccarron

2007 23LSV 340 Monsoon Misfire...

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Mmccarron

I have searched and searched in an effort not to have a repeat thread. This weekend we took the boat out ran fine all weekend, last night i noticed the boat took a little longer to fire up. Today went back out and noticed it also took a little longer to fire up. Started across the lake and had cylinder 4 misfire code come up. Killed the boat along with the battery disconnect, restarted immediately noticed under load just before getting up on plane the engine ran very rough. 2 weeks ago i replaced the cap, rotor and spark plugs. Cap and rotor are from my local dealer (actually very affordable) boat has ran great for about 16 hours until today. I tried to eliminate the wires (as they are original) by swapping the cylinder 4 wire with another to see if the misfire moved, well it did not. Still have cylinder 4 misfire. The boat has always fired right up even from a cold start first thing. Once i get up on plane the engine runs smooth. I always run 93 fuel or 92 ethanol free. The plug wire in question has a ohm reading of 5.9, from what i have seen from others that is pretty decent. Plugs are the 41-993 AC Delco. Boat has 367 hours as of today. 

Has anyone had an issue similar to this? 

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JLT3

I sort of had a similar issue where it would idle fine and then upon acceleration I would get a backfire.  Replaced cap, rotor, and plugs and it did not help.  I then replaced fuel filter and that did not help.  Finally found out that fuel pressure was around 35-40PSI and thus replaced the fuel pump.  Fuel pressure is 50+ PSI now and boat runs great.  Might check the fuel pump next but seems strange that only one cylinder is having the issue.

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Mmccarron

That’s what I am thinking. I am lost because it is only cylinder 4. Talked with the dealer this morning, they said possibly a cracked head...

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Steve B.

Try swapping a known good spark plug. See if it still follows that cylinder.

Steve B.

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Mmccarron

I will try that this afternoon or tomorrow hopefully. I do not think cracked head is the case because it can be intermittent. I was able to drive yesterday after messing with a few things with no issues then the engine fault appeared with this same code.  

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Mmccarron

Update: I removed the less than 3 week old spark it looks perfect. Installed brand new and still have misfire code. I am at the point of pulling the boat off the lift and bringing it to a shop. Any help is much appreciated!!

Plug pic: https://www.dropbox.com/s/frnt0a1fdord8wl/IMG_1372.jpg?dl=0

 

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formulaben

I would check the coil.  Can't say for sure on your model, but a new one for my engine was pretty cheap.  Too many threads here of people having issues and after lots of time and money spent it ended up being a bad coil, so I replaced mine due to its age.  If original, that coil on your boat is now probably 13 years old...

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Mmccarron

I am confident it is original. I was thinking about replacing the coil but thought I would see more misfires on other cylinders is the coil was bad. Thanks for your input!!

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formulaben

Also there were some posts here about someone having a similar issue.  They went to copper top plugs and fixed it.  I'll see if I can find that post.

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csleaver

The ECM uses the crank position sensor to measure changes in rotational velocity of the crankshaft at steady state to sense misfires.  Anything that causes a change in the crankshaft rotation when holding the throttle steady can result in a misfire DTC.  That said, any issues with the ignition or fuel systems (spark plugs, wires, cap, rotor, cam angle / timing, fuel pressure, fuel condition, injectors, low cylinder compression) can cause a misfire.  Vibrations can also fake out the ECM to think there is a misfire, like from poor alignment or a bent prop shaft.  Even a loose or damaged prop, sea pump bracket, crank sensor, reluctor, vibration dampener or flywheel dampener can be seen as a misfire.  Start with the easier stuff first and then work your way towards the harder stuff until the misfire issue is resolved.

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Mmccarron

update: i meant to post this last week and forgot. I replaced the cap and rotor (again) no change. I ended up pulling the intake and checking the injectors, put everything back together and it seemed to run perfect for the 30 min trip I took it out on. I will see as soon as the weather clears up if it is actually gone. I also replaced the tiny fuel filter located on the top of the fuel pump (pretty sure it was original) i also checked the compression on all cylinders 180 across the board. 

 

thanks for the info from everyone!

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prwkbrder

Any update on this?

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madddc

I changed my spark plugs after a misfire code, and everything is running great. How do I clear a "service required" pop up? 

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Eagleboy99

A lot of times, codes can be cleared by disconnecting the battery.  Works for some cars; not sure it will work here though.

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csleaver

Most MEFI5/6 ECMs require three engine heat cycles to clear a Type A DTC.  That means starting the engine and letting it run until the coolant temperature is above about 140 degrees F, and then shutting off the motor and waiting until the coolant temperature is below about 140 degrees F, and then repeat that two more times.  Or, use a diagnostic tool like Diacom to erase the Previously Active Trouble Code, then turn the ignition off for at least 30 seconds.

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