The engine pinks at 2000 RPM when warm. I've tried a wide range of fuels, with & without added ethanol, 87-91 octane, and the fuel seems to make no difference.
No pinking at all when cold, but reliably pinks when warm under load.
I haven't replaced the spark plugs yet, but they are next on my list.
Any thoughts on cause & solution?
There are quite a few threads here on engine "pinging". Some people's engines ping and others don't. Lot's of discussions... no conclusions. If you reset your ECU (pull the battery cables off for a few minutes) then it probably won't ping for a while until the engine re-learns and leans the mixture out for optimum EPA requirements.
The engine has a 5 year warranty so let it ping away. If it doesn't eat a valve seat in 5 years your'e probably OK for the duration.
I solved my pinging problem with new mud terrain tires. They make so much noise I usually can't hear the engine ping.
Funny! I always thought that the OP's problem was just and only called pinging, but I've just learned that pinking is also acceptable.
Like the great Benny Hill always said,...."Learning all the time!"
Wow I learned something new. I thought pinking was a type error.
Knocking (also called knock, detonation, spark knock, pinging or pinking) in spark-ignition internal combustion engines occurs when combustion of the air/fuel mixture in the cylinder starts off correctly in response to ignition by the spark plug, but one or more pockets of air/fuel mixture explode outside the envelope of the normal combustion front.