Chevrolet Repair Questions? Ask a Mechanic for Answers ASAP
Normally you replace a rotor and a distributor cap as a pair. Did you replace the cap as well?
There are numerous causes for misfiring, it could be the ignition, it could be a fuel injector dripping fuel, it could be a vacuum leak because of a leaking intake manifold gasket, it could be a mechanical problem with the engine such as a worn camshaft lobe, valves not seating because or carbon buildup on the valve stems, etc.
Do you know which cylinders are misfiring and when, at idle, while reved up, only when cold/hot, etc?