Oxygen Sensor and misfire
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Elder User
Joined: Oct 2001
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From: Cypress, CA
Oxygen Sensor and misfire
I need help understanding how this can happen. The situation is my 1998 Contour with a Zetec 4-cylinder. Son called me with the CEL on and I got codes PO336 and PO341 which is the #2 o2 sensor failure. By the time we had a chance to work on it the car developed a "miss" and set an additional PO304 which is a misfire on cylinder 4.
Turns out when the rubber hits the road that he bottomed the car on a steep driveway and smashed the wiring that feeds the o2 sensor #2. We managed to get that challenge cleared along with a pointed discussion. Once we restarted the car with all 4 wires making contact of course the PO336 and 341 went away but also the 304 and the miss went away.
How does the o2 sensor effect only one cylinder or am I really missing something here.
Any insight will be appreciated.
Russ
Turns out when the rubber hits the road that he bottomed the car on a steep driveway and smashed the wiring that feeds the o2 sensor #2. We managed to get that challenge cleared along with a pointed discussion. Once we restarted the car with all 4 wires making contact of course the PO336 and 341 went away but also the 304 and the miss went away.
How does the o2 sensor effect only one cylinder or am I really missing something here.
Any insight will be appreciated.
Russ
Post Fiend
Joined: May 2006
Posts: 10,007
Likes: 4
From: Central Florida
Its probably a DIS ignition like the 4.6/5.4, and possibly shorting out the ground return on the o2 harness shorted out that coil driver. Or it could have shared a ground with that coil or injector, so when the wire shorted it had a pos on the neg terminal and the triggering pos failed to have an effect.
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Elder User
Joined: Oct 2001
Posts: 724
Likes: 0
From: Cypress, CA
Great thought ReAX - turned out to be a bad spark plug wire. Could not detect any problem and the wires tested O.K. for resistance. New wire set solved the issue. Go figure. The fact that it stopped missing for a while after the o2 sensor wires were repaired is a fluke...
We live and learn
Russ
We live and learn
Russ
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