Can a cylinder misfire triger an O2 sensor code?

[Ocelot]

I had a problem today with some rough running and the truck threw two codes. I had a P0308 cylinder 8 misfire which explains the rough running, but I also had a P2098 code which is post catalyst fuel trim system too lean on bank 2.

Could the misfire cause the O2 code also or is is just a coincidence and two separate issues?

I was in town and picked up a coil pack and a set of upper spark plugs and of course the truck seemed to run fine on the way back home, which is why I said temporary problem. I did replace the #8 coil pack and all 8 upper spark plugs and a 8 mile test drive was fine without throwing any codes.

The truck is a 2011 and I only have 61,000 miles on it, but it could be time to replace the O2 sensors anyway. I have a trip next week towing my camper and I'm hoping the coil pack and plugs took care of it.

Ray

 

[Elevated 2013]

I would think it’s possible for a cylinder misfire code to throw an O2 sensor code but more likely the other way around because the PCM is trying to lean out or add more fuel to a cylinder to compensate for an issue that it thinks is happening. Not generally the other way around unless the O2 sensor is reading too rich because the engine isn’t able to burn as much fuel as it should be. Does that make sense??


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[madtrucker2016]

Try looking at the Map Sensor

 

[Ocelot]

That's what I was thinking also, that the O2 sensor would be more likely to read rich from a misfire. Also, this was the post catalytic sensor although it was on the same side as cylinder 8.
The truck ran great again today for the 20 miles I drove it after replacing the upper plugs and the number 8 coil pack and neither the misfire or the O2 sensor code came back.

I will check the MAP sensor as well and I ordered two post catalytic O2 sensors to keep on hand.

Ray

 

[Elevated 2013]

It never hurts (except for your knuckles and wallet) to replace O2 sensors as part of a tune up as they do start to read a little off as time goes on. I used to do it more often but I’ve kind of stopped except when theres a code or my gas mileage is way off and everything else looks good.


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[Kap1]

I've had this co2 sensor imbalance between the two bays Cel before. Mine was traced to a leaky manifold, or maybe it was cylinder misfire. Can't recall for sure but check out both..

 

[Ocelot]

I've had this co2 sensor imbalance between the two bays Cel before. Mine was traced to a leaky manifold, or maybe it was cylinder misfire. Can't recall for sure but check out both..

I'll also check for leaks, but I did have the misfiring on cylinder 8. As far as I know, the post catalytic O2 sensor shouldn't have any effect on performance, even if it goes bad since I think only the first O2 sensor before the converter changes the fuel mix if it detects a lean/rich condition. I think the post catalytic sensor just monitors and throws a code but doesn't change anything. Though I could be wrong about that.

Ray

 

[joshuaeb09]

I'll also check for leaks, but I did have the misfiring on cylinder 8. As far as I know, the post catalytic O2 sensor shouldn't have any effect on performance, even if it goes bad since I think only the first O2 sensor before the converter changes the fuel mix if it detects a lean/rich condition. I think the post catalytic sensor just monitors and throws a code but doesn't change anything. Though I could be wrong about that.

Ray

Post cat o2's are to check catalyst efficiency pre cat o2's are part of the fuel strategy. On past vehicles I've had both go bad after a while so if I've got to replace one I usually replace all of them so I don't crawl back down there a 2nd time.

 

[Elevated 2013]

The post O2 sensor can also be a good tool to use to determine if your cat is on its way out and time to be changed if replacing the post O2 doesn’t fix an issue.


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[Ocelot]

The good news is that since I replaced the #8 coil and all the top plugs, there hasn't been anymore codes, including the O2 sensor. No issues towing my camper which is about 5,000 loaded 100 miles yesterday over lots of hills.
Thanks everyone for the advice.

Ray

 

[Elevated 2013]

Great!! Glad to hear that!!


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