That is not a good sign. That is exactly where the bearing problem starts that I had and Coach just experienced. I replaced my engine with a new 3.5 from Isuzu. Coach is currently swapping a 5.7 liter GM engine (fingers crossed). Take it and get it checked immediately by a reputable mechanic or the dealer. Not something to take lightly. I hope it is the coil pack or a plug and not an internal engine problem.