Thanks for all the replies so far. Mileage is 175k miles. Past history mostly unknown. I bought the truck last November. Except for this spark knock when it's real hot out, the truck really runs like new. It has a lot of power for a 4-cylinder. It doesn't outrun Camaros or anything, but it easily keeps up with traffic. I do use that gas pedal, though, and if I have to be easy on it (1/4 throttle) to keep it from knocking, it DOESN'T keep up with traffic very well.
Good tip on the combustion chamber deposits. I have prior experience with GM Top Engine Cleaner -- that stuff really works. It isn't without risk, though, and I don't know the condition of the head gaskets on this Nissan. That Top Engine Cleaner puts a lot of pressure on the head gaskets I think, and I don't want to try it yet, not if I don't have to. I'll get a cap and rotor and maybe a set of wires -- and I'll check the timing.
By the way (CarGuy), North Carolina is great... We live in Fayetteville and I work at the Ft. Bragg Army Installation as a civilian contractor (in their Environmental Compliance office). Ft. Bragg is about 200,000 acres spanning five different counties -- and there's a lot of artillery training going on here all the time. You can hear it a lot at the house...they call it "Bragg Thunder". I hear, though, that this isn't anything compared to when the Marines come to train in March and October -- they bring out the BIG GUNS. Ft. Bragg is also home to the 82nd Airborne, the Army's elite group of paratroopers. They have jump schedules publicized and you can go watch them. We're excited to do that. They have a jump scheduled next Saturday...we're gonna take the Nissan out there and get out in the dirt and get dirty and watch some paratroopers.
