You have nothing to lose, give it a high rpm 'tune up' after warming the engine up a little. I suspect you have a valve that isn't closing.

You also might want to do a Seafoam treatment to clean out the combustion chambers. Use a vacuum line that is attached to the vacuum tree, by the throttle body, and let the engine 'sip' a little Seafoam until the engine rpms bog down. Do not let the engine suck up a lot of Seafoam all at once!! Too much liquid will break a wrist pin! Just dip the vacuum hose in the bottle 1 second at a time. You can pour the remaining Seafoam in the gas tank.

Your cheap gasoline does not contain any cleaners, burns too fast, retards the timing, and the short commute never lets the oil temperature rise to above boiling. Ie., cold engine running at low rpms and cheap gasoline = cylinder carbon.

Klaus

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Always willing to listen, just not able to take direction.