Chris 
2002 Nissan Altima Sedan 2.5 SL 4dr Sedan (2.5L 4cyl 5M)
Worst Engine by Nissans Ever
 Only consider purchasing a 3.5L engine do not buy a 2.5L 4 cyl lemon!!! These engines have problems with pre-cat manifold, bolts from intake manifold can potentially enter the cylinders, crank/cam position sensors go bad, heating/AC problems. Other then that the car is great, really liked brakes and suspension, and gas mileage which varied from 21 to 27mpg. I bought the car around 75k-80k miles and it was already loosing oil since I fortunately noticed it right away after I bought it. Car had pre-cat replaced under warranty right before I bought it but the damage to engine from intake bolts or pre-cat was already done. The car mysteriously was losing 1qt of oil every week, after full 