2002 Sable with the V6 duratec engine.Check Engine light had come on and blinking. Autozone read the codes and said bad O2 sensor and something to do with Cylinder#6. I replaced the O2 sensor and cleared the codes. Car starts fine and seems to run fine, no check engine light. The question is this. While in park I can only rev the engine to about 4000rpm, at 4000rpm the engine statrs to miss real bad, but if I'm driving the car the motor will rev well above 4000rpm. 5000-5500 rpm without a problem. Does the car have some type of rev limiter preventing me from going above 4000rpm while in park? Or do I still have a problem wit the car. Also i pulled the plug to cylinder#6 and dont see any problems. Car has 50K miles on it.