Bought a used Xterra 2001 (100,000 miles), working fine for first two months but after a long trip it started stuttering sometimes at around 2500 revs, specially when hot. The engine also went dead a few times while waiting in traffic light. In Advance Auto they said it was misfiring, knock sensor, recommended to change it. Mechanic on the other hand said it the distributor wasnt working properly. Bought one and replaced it my self thou I havent done the timing (dont know how to do it). When I took off the older one it was covered by oil and metal particles on the bottom. (I think since it was covered with particles It wasnt rotating adequately) The engine starts perfect but now I have stuttering on idle, low revs, could it be because of the timing?