I've got a John Deere x738 with 60 hours on it. About two weeks ago on start up I could tell it was different. The engine vibrated a lot more and the engine seems to be misfiring. When the engine starts its fine, but about 10 seconds after startup it beings acting this way. It clears itself up after about a minute or two. This does not happen if the engine has already been running and is restarted. The machine only runs on ethanol free gas and is kept in an attached unheated garage.
Things I've done already:
- oil and oil filter change and used Mobil 1 synthetic 10W-30 (old oil was John Deere version and very black and only in the machine for 50 hours)
- charged the battery (it was fine though)
- disconnected the battery and reconnected the battery (to possibly reset any electrical problems)
- checked hoses and wiring (saw no issues)
- added Sea Foam (can't hurt)
- changed fuel filter
- changed air filter and prefilter
- changed spark plugs
When I changed the spark plugs I saw they were in terrible shape, completely black and wet (see pics). It's at the dealership now but I am afraid they are going to say nothings wrong. Has anyone experienced anything similar to this?