Hello I have a 2013 Chevy Suburban with 215k miles and a very light misfire at idle and highway speeds. The misfires are so light that I wonder if I'm blowing it all out of proportion and its actually okay.
Some important info:
1. The check engine light does NOT come on. The misfires are found through my Ancel code reader. I have had cases where every cylinder has registered a misfire before EXCEPT cylinder 4 oddly. That one runs pristine.
2. The misfires are few and far between when at highway speeds. I may accrue up to 10-15 total misfires across 8 cylinders over a 45 minute drive. Cylinders 3 and 5 are the biggest offenders, but cylinder 8 can also have a few. I thought I caught one yesterday when AFM was switching from V4 to V8, but its nearly impossible to prove that this is what it was.
3. The "idling" misfires are hot idle misfires (at engine coolant operating temp of 200 degC). I can actually feel the steering wheel jerk when it is idling, but it is very slight. I can have 2+ misfires accrue on the computer over the span of a few minutes on cylinder 8. There is a broken exhaust bolt on cylinder 7, causing a slight exhaust leak, so this may be the culprit? Can't tell. My idle drops really low as well, probably near 500 RPMs. I've heard this is an issue with these engines that the idle is set super low for emissions reasons.
Things I have done so far:
1.Compression test: All cylinders (except Cylinder 2): 175 PSI, Cylinder 2: 190-195 PSI. Not at all sure why Cyl 2 is high, maybe carbon deposits? But I ran a can of Seafoam through the intake...
2.New spark plugs 6k miles ago. No new wires or coils that I installed, but the previous owner put Belden wires with heat shields on.
3.Engine has been running rich for the past few weeks due to a different issue where my fuel trims were reading 70% ethanol content, but when we pulled the plugs to check compression (after we had solved that issue), they weren't majorly dirty. Some were wet, some where a little white, some were a little dark. None were black, cracked, burnt or ashy.
4.Replaced PCV Valve because oil was pooling in my intake. Oil is still pooling in my intake after replacing it. Oil could be getting into the cylinders, but as I said the plugs aren't super dirty.
I am probably blowing this all out of proportion, but as someone who wants to work out all the kinks in this wonderful vehicle, it does drive me insane knowing I have random misfiring happening.
Some important info:
1. The check engine light does NOT come on. The misfires are found through my Ancel code reader. I have had cases where every cylinder has registered a misfire before EXCEPT cylinder 4 oddly. That one runs pristine.
2. The misfires are few and far between when at highway speeds. I may accrue up to 10-15 total misfires across 8 cylinders over a 45 minute drive. Cylinders 3 and 5 are the biggest offenders, but cylinder 8 can also have a few. I thought I caught one yesterday when AFM was switching from V4 to V8, but its nearly impossible to prove that this is what it was.
3. The "idling" misfires are hot idle misfires (at engine coolant operating temp of 200 degC). I can actually feel the steering wheel jerk when it is idling, but it is very slight. I can have 2+ misfires accrue on the computer over the span of a few minutes on cylinder 8. There is a broken exhaust bolt on cylinder 7, causing a slight exhaust leak, so this may be the culprit? Can't tell. My idle drops really low as well, probably near 500 RPMs. I've heard this is an issue with these engines that the idle is set super low for emissions reasons.
Things I have done so far:
1.Compression test: All cylinders (except Cylinder 2): 175 PSI, Cylinder 2: 190-195 PSI. Not at all sure why Cyl 2 is high, maybe carbon deposits? But I ran a can of Seafoam through the intake...
2.New spark plugs 6k miles ago. No new wires or coils that I installed, but the previous owner put Belden wires with heat shields on.
3.Engine has been running rich for the past few weeks due to a different issue where my fuel trims were reading 70% ethanol content, but when we pulled the plugs to check compression (after we had solved that issue), they weren't majorly dirty. Some were wet, some where a little white, some were a little dark. None were black, cracked, burnt or ashy.
4.Replaced PCV Valve because oil was pooling in my intake. Oil is still pooling in my intake after replacing it. Oil could be getting into the cylinders, but as I said the plugs aren't super dirty.
I am probably blowing this all out of proportion, but as someone who wants to work out all the kinks in this wonderful vehicle, it does drive me insane knowing I have random misfiring happening.
