I recently traded my '00 Ranger for a '01 Galant V6 (auto) LS. The other day I noticed a "loping" sound as I accelerated my car through the gears. It's only when the car is under load I can hear the "loping" but not when the car is in park or when I'm at a stop (idle). Btw, when the car is in neutral/park the motor revs fine w/out any loping. Also, when the car is in gear and I'm at a complete stop I can hear a very low level but loud harmonic resonance throughout the car (almost like very deep bass). If I put the gear into neutral/park (i.e., no load on the motor) the harmonic resonance goes away. The idle is a couple hundred RPMs too low. Suggestions?