I was driving and i was loosing power so I pulled over while my civic was running and it didnt have an alternator belt on then i look at the pulley (harmonic balancer and it shaking to the left and right really bad but the bolt was tight. I shut off the car and see that my timing belt was coming off because it was burning through the timing belt cover which is made out of plastic. Luckily it didnt come all the way off. I took the pulley off and guess I need to replace it but why did the timing belt start to come off? From the pulley shaking the whole crankshaft? Or is it a separate problem. A new pulley from honda is 108.00. Why would a pulley go bad? I dont see any gaskets or anything but inside the hole that goes over the crankshaft where the tooth [ ] locks in there is alot of unusual wear so I knnow to rplace it. Wondering what caused it?