It seems I have a problem with my DOHC Neon. I have a code 12 and 43.
Originally I had only a code 37 (I believe it was), which was for the radiator fan relay, which I replaced.
After that, I cleared the codes, then got the codes 12 and 43. I replaced the coolant temp sensor, and the code cleared, but it is now back.
I have what feels like a misfire in acceleration. I have also replaced my spark plugs, and the old plugs looked fine, maybe a little lean, but otherwise ok. The wires are fine.
The car starts fine in the morning, and doesn't feel like it is going to die, it just has a shuddering at certain speeds or under load. The CEL flashes when this occurs as well.