High Oil Pressure / Misfire

Bentley · June 11, 2024

HawaiianRR: Brilliant!

OK, you may have convinced me to do this job. At least I may pull out the lifter(s) and inspect.

Bentley · June 11, 2024

HawaiianRR: Can you tell me how you inspected your cam?

HawaiianRR · June 11, 2024

Just now, Bentley said:

HawaiianRR: Can you tell me how you inspected your cam?

I’m definitely not a mechanic, but I have lots of the necessary tools to work on cars. Follow some yt videos and you’ll be fine.
I took out the lifters and you can see into the hole where the lifters are and I used a scope camera to get a better look if there was scoring. Plus the broken lifter I took out, that roller was not damaged.

Bentley · June 12, 2024

HawaiianRR: I think you've convinced me not to swap motors right away. Keep me updated on how it goes. Thx.

HawaiianRR · June 12, 2024

1 hour ago, Bentley said:

HawaiianRR: I think you've convinced me not to swap motors right away. Keep me updated on how it goes. Thx.

For sure. I’d definitely check to see how your lifter and camshaft is first.
Today I ordered about $600 worth of GM OEM parts to go back in. Hopefully it all works as it should, if so, I’ll be happy with less than a grand to get this thing back on the road. If it happens again, maybe ill considered parting this ****** out or go try and cross a deep creek lol

stoltz423 · January 20, 2025

Anyone have these issues and found a solution?

Our 2017 6.2 Sierra started something similar last winter, mainly when it was below freezing and wet (going thru a carwash in the winter). Check engine light comes on and will flash, traction control will come one and engine will run rough. Code reader shows a misfire. I believe it was cylinder 8 last winter.

Fast forward to this winter and it's back. This time cylinder 5 misfire. This happened to us on Christmas eve when driving home (12 hour trip). Given the situation we had not choice and decided to continue driving thru it. For about 4 hours (until the roads dried up) the check engine light was on and would occasionally flash. When this started the traction control light was also on. However the Traction Control light would come and go. Every time the Traction Control light came on the oil pressure would rise (10 PSI or so) and as soon as the traction control light would go off, the oil pressure would drop back to normal. This was a clear repeatable pattern.

I have had a few people look at the truck including the local GMC dealership and they can't recreate the issue. Also they tell me no codes are saved that are any help.

I feel the issue is something electrical as it's triggered by low temperatures and moisture. The traction control light and oil pressure increase has me stumped.

I should note that the truck returns to normal once the Check Engine light goes off. We have put probably 15K on it since the issue first started last winter.

Edited January 20, 2025 by stoltz423

newdude · January 20, 2025

59 minutes ago, stoltz423 said:

Anyone have these issues and found a solution?

Our 2017 6.2 Sierra started something similar last winter, mainly when it was below freezing and wet (going thru a carwash in the winter). Check engine light comes on and will flash, traction control will come one and engine will run rough. Code reader shows a misfire. I believe it was cylinder 8 last winter.

Fast forward to this winter and it's back. This time cylinder 5 misfire. This happened to us on Christmas eve when driving home (12 hour trip). Given the situation we had not choice and decided to continue driving thru it. For about 4 hours (until the roads dried up) the check engine light was on and would occasionally flash. When this started the traction control light was also on. However the Traction Control light would come and go. Every time the Traction Control light came on the oil pressure would rise (10 PSI or so) and as soon as the traction control light would go off, the oil pressure would drop back to normal. This was a clear repeatable pattern.

I have had a few people look at the truck including the local GMC dealership and they can't recreate the issue. Also they tell me no codes are saved that are any help.

I feel the issue is something electrical as it's triggered by low temperatures and moisture. The traction control light and oil pressure increase has me stumped.

I should note that the truck returns to normal once the Check Engine light goes off. We have put probably 15K on it since the issue first started last winter.

Sounds like bad wiring at the front of the engine. Oil pump solenoid harness or the jumper harness it plugs into.

Bentley · January 20, 2025

Mileage/kms ??

You are describing my (old) engine exactly.

On a scan, the oil pressure spikes BEFORE the misfire. This seems to indicate non-electrical, that is a mechanical defect.

You can read my thread for details, but I replaced many parts - including oil pump - as I thought it might be the relief valve in the pump being faulty.

In the end, it was a bad lifter, which ruined the cam, and quite possibly hurt the valve.

Considering the high mileage on my truck, I just received my new engine. For me, the rebuild option did not make sense.

Lots of info on low oil pressure but not on high oil pressure.

My theory: The bad lifter is causing the computer to increase oil, or at least leak oil. This influx of oil works on the back end of the pump to offset the relief valve, thus causing high oil pressure. Just a theory, not looking for arguments.

stoltz423 · January 20, 2025

12 minutes ago, Bentley said:

Mileage/kms ??

You are describing my (old) engine exactly.

On a scan, the oil pressure spikes BEFORE the misfire. This seems to indicate non-electrical, that is a mechanical defect.

You can read my thread for details, but I replaced many parts - including oil pump - as I thought it might be the relief valve in the pump being faulty.

In the end, it was a bad lifter, which ruined the cam, and quite possibly hurt the valve.

Considering the high mileage on my truck, I just received my new engine. For me, the rebuild option did not make sense.

Lots of info on low oil pressure but not on high oil pressure.

My theory: The bad lifter is causing the computer to increase oil, or at least leak oil. This influx of oil works on the back end of the pump to offset the relief valve, thus causing high oil pressure. Just a theory, not looking for arguments.

170K today but when it started last winter it was around 155K. Maybe my thinking is wrong but if there was something internal wrong with the engine, lifter, cam, etc. would it have gone all year and 15K without issues? Seems to only happen when it's below freezing and there is a lot of moisture in the air.

Bentley · January 20, 2025

I was a little fooled at first with weather temp.. In my case the lifter 'bearing' was shot. Like any bearing, I am sure that the fail is sporatic at first until it fails completely. Maybe in cold weather it contracts - Idk?

If the cam is still good, you are fortunate. FYI - if you replace lifters, do all of them, and replace the VLOM.

stoltz423 · January 20, 2025

13 minutes ago, Bentley said:

I was a little fooled at first with weather temp.. In my case the lifter 'bearing' was shot. Like any bearing, I am sure that the fail is sporatic at first until it fails completely. Maybe in cold weather it contracts - Idk?

If the cam is still good, you are fortunate. FYI - if you replace lifters, do all of them, and replace the VLOM.

Good to know.

Are you saying yours was weather/temperature dependent also?

Also did your Traction Control and CEL lights come and go or once it started the lights stayed on till you got your new engine?