Got a weird one helping a friend tonight...
Both upstreams O2's switching normally and respond properly to rich and lean conditions at idle and pretty well match for both bank of cylinders and function normally above idle.
S/T is within 4% L/T is within 10%
Both downstream O2's stable above idle and match almost identically but one O2 post catalytic on one bank of cylinders goes extremely lean at idle after about a minute idling while the other sits at its normal stable level. While this is happening the up-stream for that same bank is cycling normally and matches more or less the other bank where it isn't going lean at idle.
The plugs on the vehicle all look like they have similar burn between cylinders and there is no misfire counter for any cylinder. The idle could be smoother so I think it might be operating a tad bit lean.
My thought is either a lying upstream on that bank of cylinders driving the mixture leaner than it should be at idle and thats why we can see it in the converter's readings, a fuel injector not putting out enough at idle driving the readings lower post catalytic, or there is an exhaust leak prior to the converter and it's drawing in some extra air which is why it doesn't show up unless it's at idle when the flow is lower. I don't believe this last one is the cause because the temperature in that catalytic is dropping at idle indicating a lack of fuel.
The reason it's a problem is the temperature will be correct on the catalytic converter on this affected bank above idle but at idle it starts to drop off as it begins to read lean.
I'd ask my dad but he's not in a great condition tonight... Thoughts?
2015 Jeep with the 3.6L Engine 68,000 miles (109,000km)
Both upstreams O2's switching normally and respond properly to rich and lean conditions at idle and pretty well match for both bank of cylinders and function normally above idle.
S/T is within 4% L/T is within 10%
Both downstream O2's stable above idle and match almost identically but one O2 post catalytic on one bank of cylinders goes extremely lean at idle after about a minute idling while the other sits at its normal stable level. While this is happening the up-stream for that same bank is cycling normally and matches more or less the other bank where it isn't going lean at idle.
The plugs on the vehicle all look like they have similar burn between cylinders and there is no misfire counter for any cylinder. The idle could be smoother so I think it might be operating a tad bit lean.
My thought is either a lying upstream on that bank of cylinders driving the mixture leaner than it should be at idle and thats why we can see it in the converter's readings, a fuel injector not putting out enough at idle driving the readings lower post catalytic, or there is an exhaust leak prior to the converter and it's drawing in some extra air which is why it doesn't show up unless it's at idle when the flow is lower. I don't believe this last one is the cause because the temperature in that catalytic is dropping at idle indicating a lack of fuel.
The reason it's a problem is the temperature will be correct on the catalytic converter on this affected bank above idle but at idle it starts to drop off as it begins to read lean.
I'd ask my dad but he's not in a great condition tonight... Thoughts?
2015 Jeep with the 3.6L Engine 68,000 miles (109,000km)
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