2003 f-150 4.2 getting an oygen sensor fault, need help!

Question

I'm starting to get a bank 1 oxygen sensor code running lean with my truck. I'm trying to figure out what's causing it. I've noticed that at idle, the rpm (especially when the ac is on) will loop up and down by about 300 rpms. Any help is appreciated.

Answer 1

step one, don't read the first answer without looking for the problem as $1000 later you will kick yourself.

Usually a lean code on them trucks came to be from a intake air leak between the upper plastic intake and lower aluminum intake from the o-rings and rubber around the bolts for the intake...

Ford dealers all know about this but don't have the bulletin that spells out the issue

Answer 2

WELL WHY DONT U REPLACE UR OXYGEN SENSOR IT CAN HAVE 1 OR 2 SENSORS I BELEIVE YOURS HAS 2 THE ARE CONECTED TO THE INTAKE MANIFOLD. ALSO IT COULD BE YOUR INTAKE MANIFOLD OR YOUR CATALITIC CONVERTER. IF YOUR CAR HAS OVER 100000 MILES AND YOU HAVENT CHANGED THE CATALTIC CONVERTER THAT CAN BE YOUR PROBLEM. GO TO AUTOZONE YOU CAN RENT THE CODE SEARCHER AND THEY CAN GIVE YOU ADVICE THERE.