Bad gas?

[Jon K]

I get it from time to time usually after mexican or chik fil a

[JD525IA]

I know what you are thinking, but, no I am not gassy and bloated, usually.

I filled up with fuel this morning and within 1/4 mile of leaving the station, my car suddenly had a CEL and was running like one of the cylinders had just stopped working. It was very rough, with the tach idle level going from about 750rpm down to nearly 350rpm. I was able to rev the engine up once I put it into neautral but it was even revving rough.

I was half way to work at this point but I turned around and went home. I didn't want to shut it off in case it would not restart. I did the stomp test at home and got 1221 - #1 Oxygen sensor. My sensor is not that old and I have not had any decline in performance or mileage lately. Do Oxygen sensors just suddenly go bad?

I thought the gas I had just purchased was the cause right off the bat. I did a bunch of checking under the hood and found nothing. I decided to go ahead a change the spark plugs that I was planning on changing in the next couple weekends. It did smooth out the idle a bit, but the CEL was still there.

I decided to go to work and get a Oxygen sensor on order during lunch. By the time I reached my freeway exit, I had put about 60 miles on the new tank of gas. When the light at the exit changed, my CEL went away and the engine began to run like before my initial problem started.

Could it be that there was water in the new gas and it took the 60 miles of driving to get rid of it? Or could it be that the refineries have gone to a more ethanol-rich mixture that the car could not handle right off?

I've never had a problem like this with this car.

Help.