Why does the car have a Rough Idle?
Assuming youíre talking about a "rough" idle that reads around 500 to 700 RPM on the tachometer, Welcome to the World of Longer-duration Camshafts and V-10s! Your rough idle is actually normal. First of all, the Viperís V-10 motor has 10 cylinders firing onto a 90-degree crankshaft, which means it has an uneven firing interval for two of the ten cylinders. In other words, the spark plugs donít all fire in equally spaced time intervals. So thereís one cause of an un-smooth idle. Secondly, the camshaft duration is 220 degrees (@ 0.050" lift), which translates into a motor that prefers to spin happily (and efficiently) an higher RPMs. And, subsequently, doesnít operate very "smoothly" at low RPMs.