A 2000 Toyota Celica GTS 225k miles engine makes a mild rumbling/grumbling rough sound when accelerating slowly from a stop in drive or reverse only in the 800-1300 RPM band. Does not occur when in Park. Not sure what could be causing this mystery.
Already changed (with OEM Toyota parts) Exhaust gaskets, Plugs, all 4 motor mounts
Sounds almost like something in the engine is loose, pistons, value chatter, I am lost for an answer.
Hopefully someone has a thought, Thanks!