'02 Silverado 4.3L.
Was running bad and throwing random cylinder misfire and oxygen sensor codes. I replaced the injectors with the new MFI style. The codes were cleared after swap. It ran great for about 200 miles.
Truck began missing and running about like it did before injector swap. Random cylinder misfire and O2 codes returned. I pulled downstream O2 sensors, cleaned with MAF cleaner and replaced (may have reversed them from original installation order, not that it should matter).
The missing got worse each time I restarted the truck from here on out. It won't stay running now, and acts like it is flooding out.
The cats and oxygen sensors are likely toasted from driving on the P0300 for so long to begin with. But would bad O2s make it throw random cylinder misfire and run so poorly? It has been throwing these codes for a while and has never been so bad.
Another thought that comes to mind is that during injector swap I had to pull the injectors out of their holes a few times and the plastic "clips" that hold them in my have worn out some, causing them to get lose. Could the engine have backfired and blown an injector out of its hole in the lower plenum?