Bought it in 2014. Now have 135,000 miles. Had a SES light intermitant since Oct., Last week began flashing with a very obvious misfire. Presumed it would be timing belts. OBD said misfire #4 . found worn plug wires. replaced plugs, wires, cap, rotor. Runs better, but still not totally smooth. SES light again intermittant. added Seafoam then filled gas tank. hoping this works to clear cylinders and smoother running. am I on the right track anybody ?