Another code 1 question.

1991 1.5 Sedan, Automatic.
What else beside an oxygen sensor could cause a code 1? I am told that my symptons do not indicate the oxygen sensor.

Here they are. In the morning, the check engine light is not on. Around 10 minutes into the drive, the motor will run rough for around 5 seconds, then the check engine light comes on and the car smooths out and runs fine for the rest of the journey. Next time I start it, the sequence starts all over again. I have also noticed that my fuel economy has gone way down.

So any help would be greatly appreciated.
Thanks

1991 1.5 Sedan, Automatic.
What else beside an oxygen sensor could cause a code 1? I am told that my symptons do not indicate the oxygen sensor.

Here they are. In the morning, the check engine light is not on. Around 10 minutes into the drive, the motor will run rough for around 5 seconds, then the check engine light comes on and the car smooths out and runs fine for the rest of the journey. Next time I start it, the sequence starts all over again. I have also noticed that my fuel economy has gone way down.

So any help would be greatly appreciated.
Thanks

Hooray!!! I was getting ready to replace the oxygen sensor and found the wire broke. Maybe it got caught in the fan??? Anyway, I repaired the wire, reset the ECU and no more problem.