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The story so far: a couple of months ago the car started running rough when cold and was sometimes difficult to start. Problem gets worse with time. I exchange the ignition coil for a brand new one and the problem goes away but comes back about 1 week later and gets worse until engine is running rough even when warm. So I exchange the whole alternator for a used one. Car starts perfectly and I turn it off again. Half an hour later I try to start it again but now it is completely dead. I put back the original alternator and the engine starts perfectly and runs fine even when cold, but for how long?