Vehicle running rich, starting issues and random misfiring when driving in town. Sometimes it says p0303 instead of p0300. I replaced the spark plugs, changed the upstream 02 sensor, replaced the 3rd cylinder ignition coil, cleaned the maf, map sensors, cleaned the intake and exhaust solenoids, cleaned the throttle body took it off and then reprogrammed
it. Vehicle runs perfect on first start up then when I shut it off and try start it back up is when it’ll crank but not turn over unless I tap the gas pedal.

I tested the pcv and seems it’s working but I have not inspected the pcv valve yet, and I think when I switched the O2 sensor I replaced the downstream one instead of the upstream one, would that Make sense that I would still be running rich and having the misfires by changing the wrong sensor? I could see the upstream one on my exhaust manifold but lower by the front passenger side tire I saw one and assumed it was the right one and that the downstream one would be by the back of the vehicle but after looking again today I see something coming out the back of the exhaust manifold that looks like the end of a O2 sensor but I haven’t gotten a good look at it as it’s in a hard to see spot

 

Fuel trims? Injector balance test? O² sensors responding? A diagnostic will put you on it.