If you have the 3.8L engine, the cam sprocket is encapsulated in nylon or a similar compound. Whe this coating begins to break down and come off, the engine will rattle like a bucket of bolts. At this point, the cam may jump a tooth or two so that it does not run and may even damage the valves. I don't recall if this is an "innterference" engine. It is not a bad jod if you have the tools and wherewithall to do the job. I have done a couple of 3.8L's and would advise that you have the oil pump rebuilt at the same time, replace the cam position sensor and install a new water pump. You will be money ahead in the long run if you intend to keep the car. I also recommend that you use an all metal replacement timing set. The only reason the nylon was ever used was to reduce noise. You will notice a faint whine fromt he timing chain at higher RPM's with the all metal set - it does not bother me.