98 Plymouth Neon problem

This morning on my way to work my neon lost power (HP). I was on the freeway and all of a sudden it started losing power, it would lose power for a couple of seconds then come back, then lose power again, etc. I pulled off the road and checked the oil (since it has had a slow leak - probably the head gasket - for a long time). It was a little low so I added some oil. It ran fine after that (I was only a couple of miles to work). The check engine light came on.

When I got to work, I checked the codes and I got a 12, 43, and 55. The 12 I understand, since I recently replaced the battery. The 43 would probably explain the loss in power but what would cause that?

Any help is appreciated.

The code 43 is a single or multiple cylinder misfire. You need to change your spark plugs with the stock Champion coppers. Also inspect, your spark plug wires and coil apck for any cracks, and replace if necessary. If there is oil on your plugs when you pull them out, don't get scared it's just your spark plug tube seals that need to be replaced. Start with the plugs and go from there.