A 2012 model with about 1300 hours on it started running rough, missing a bit after start up at idle 250 hours ago and progressively got worse but has now stablized. After warming up for 5-10 minutes at idle it will mostly smooth out and then run fine at speed and then idle fine for the rest of the day. Sometimes it takes longer to warm the rough out and it is now missing a bit at idle when I slow down between runs.
When I start the engine cold, it starts normally and idles pretty smoothly at first but when it slows to low idle after the initial 6 or so seconds of fast idle, the missing and shuddering begin.
As a bit of background, Initially, out of the box, this engine would not start on the first attempt, this was the result of faulty ECU programming which I replaced under warranty from the dealer in Juneau. Immediately after changing the ECU the engine started right up as it should, but for the first time it would shudder(run rough) for a few seconds at a time during the warm up period and on occasion after shutting down to refuel and then restarting warm. It never lasted long and never got worse but this never happened with the original ECU.
So far I have changed the plugs(they all looked fine), swapped coils and ecu with my other engine, adjusted the valves, replaced my 02 sensor, map sensor and Idle Air Control valve. Tech ran engine on his computer only code/problem noted was the IAC valve was 20% rather than what was expected that is why IAC valve replaced. No change in symptoms so I am looking for the next item to try.
I have very little time at WOT, run the motor easy most of the time at 3800 to 4200 as this is very economical and with large amounts of debris in the water and often very rough this is what is safe and comfortable. Motor runs flawlessly at speed just not so good at startup and occasionally at idle during the day. Boat used for whale watching so typically run for 45 mins, drift at idle, run 20, drift at idle, run 45, drift at idle 20 mins, run 45, repeat 3x daily, 400 hrs per season. 1300 hrs +
When I start the engine cold, it starts normally and idles pretty smoothly at first but when it slows to low idle after the initial 6 or so seconds of fast idle, the missing and shuddering begin.
As a bit of background, Initially, out of the box, this engine would not start on the first attempt, this was the result of faulty ECU programming which I replaced under warranty from the dealer in Juneau. Immediately after changing the ECU the engine started right up as it should, but for the first time it would shudder(run rough) for a few seconds at a time during the warm up period and on occasion after shutting down to refuel and then restarting warm. It never lasted long and never got worse but this never happened with the original ECU.
So far I have changed the plugs(they all looked fine), swapped coils and ecu with my other engine, adjusted the valves, replaced my 02 sensor, map sensor and Idle Air Control valve. Tech ran engine on his computer only code/problem noted was the IAC valve was 20% rather than what was expected that is why IAC valve replaced. No change in symptoms so I am looking for the next item to try.
I have very little time at WOT, run the motor easy most of the time at 3800 to 4200 as this is very economical and with large amounts of debris in the water and often very rough this is what is safe and comfortable. Motor runs flawlessly at speed just not so good at startup and occasionally at idle during the day. Boat used for whale watching so typically run for 45 mins, drift at idle, run 20, drift at idle, run 45, drift at idle 20 mins, run 45, repeat 3x daily, 400 hrs per season. 1300 hrs +