I have been having some random hesitation which only seems to happen when the car is at normal operating temp. Usually I will drive for a bit then stop somewhere and when i start up and start to go it bogs down, then when I stop at lights it sputters for a sec. I had melted a hole through one of my exhaust valves in cylinder 3 so when i was driving it, it was running hella rich and just dumping unburned fuel into the exhaust. So my question is could this have clogged up my O2 sensor causeing the hesitation? My logic behind this is that when the engine is cool it runs a tad richer until it gets to normal operating temp, then relies on the O2 sensor to make the appropriate air/fuel mixture. I am not throwing any codes either. Does this seem feasible?