In the morning or when the engine is cold I'm having misfires. This started 3 weeks ago and I changed my plugs 5 months ago with the timing belt. When I crank up my trep it will idle bad but when I step on the gas it will run fine for a min when idling then start running bad. It smokes alot also. When it's at normal operating temp it rans fine and the smoking stops. I pulled some codes that which was P0300, p0303, p0420, and p0430. Think my O2 sensors are causing misfires?
I'm using platinum NGKs. Can't find Champions anywhere anymore. That leaking fuel injector might be why I'm not getting good gas mileage now. But will it cause a misfire and just stop when the engine is warm?