2010 DF140 Rough idle and slow to build RPM's

[LakeguyGG]

Good Day,

My 2010 DF140 has a rough idle at start up and is very slow to reach 3000 RPM’s. It seems to correct itself after it is warmed up and will run good at all RPM’s until it is shut off for any length of time. I replaced fuel filters, visually inspected fuel lines and connections and checked spark plugs. Roughly 190 hours on engine and no codes have been displayed. Any input would be appreciated!

[catacom225]

How old Is the fuel and what kind of fuel are you using! Just so we can start checking things off the list

[LakeguyGG]

The fuel is roughly a 50/50 mix of last years and fresh. Last years fuel was 89 octane with a 10% ethanol blend, this year was non-oxygenated. I added stabilizer to the fuel before putting it away last fall.

[redlowrey]

Good Day,

My 2010 DF140 has a rough idle at start up and is very slow to reach 3000 RPM’s. It seems to correct itself after it is warmed up and will run good at all RPM’s until it is shut off for any length of time. I replaced fuel filters, visually inspected fuel lines and connections and checked spark plugs. Roughly 190 hours on engine and no codes have been displayed. Any input would be appreciated!

It sounds like one cyl is not working, do this simple test, remove the plug leads from each cyl one at a time when the engine is idling, there should be a noticeable drop in rpm if the cyl is working.
If you remove a lead and there is no change in rpm you have the area to start trouble shooting. First check for spark, you should have replaced the plugs, it may be a coil failing. those waste spark ignition coils can still fire on the opposite cyl, when faulty. If it make no difference to the rpm when you remove each lead and it still runs rough I will give you a different direction to take.
Start there and come back on the forum with your results

[LakeguyGG]

I put new spark plugs in and it ran like a champ. I honestly thought the old plugs looked fine but I guess I didn’t know what to look for. After installing the new plugs, I tried pulling one plug wire at a time and there was a noticeable difference for each cylinder. I hope to get it out on the water to give it a run this weekend. I will post again with the results. Thank you all for your input!

[redlowrey]

That is good that it is running on all four, but I have a gut feeling you have a coil on the way out. What happens now with the new plugs, the secondary voltage required to jump the gap is a lot lower than it needed before, say it took 25kv to jump the gap, now with new plugs it might only need 10kv so the coil is not stressed like before.

With the miss you described when cold, then coming good when hot, tells me either it is a high resistance in a coil lead, or internal tracking in one of the coils, no big deal, if it starts missing again replace the coil that the cyl is missing on.

[LakeguyGG]

Took the boat out for a test run tonight and had no issues. Thank you for your reply!