so if i warm up my 79 N/A 280zx with like 75000 miles and park it, and go back to drive it while its still semi warm, about 1 to 2 hours later, it will sometimes run rough, idling at about 500 rpm, if i try to just compensate by giving it gas, it just knocks pretty loud at around 3500 rpm, like a pistons not firing or something, after like 5 minutes of driving or so it goes away, anybody experience this problem before?