2021 tahoe 5.3 and p0308 code

I purchased my Tahoe in October of 2020 and besides the few recalls I had to take it I for, I had no complaints. As time went on, I still had no complaints but worry started to grow as the stories of the 6.0 started to grow, eventually the 5.3 afm talk started.

5yrs and 84k miles later, I was accelerating from a stop sign, heard a pop and loss of power. I pulled over and plugged in my code reader and read the p0308 & a drivetrain code.

Had it towed to my local trusted mechanic to schedule a diagnostic and compression test.
He mentioned without opening up the heads, he can’t give a definitive answer and mentioned when the engine turns on, it runs fine and once it starts to warm, valve #8 takes a dump. He doubts it’s a sensor and believes there’s an exhaust leak. He also said this year alone, he has replaced lifters on 4 5.3 engines this year and said mine seems different but can’t verify till the heads are opened up.

My question as I am no mechanic, what are the possible worst case scenarios with a ballpark price?
Would a bypass chip save new lifters if the lifters are the issue?
Link to part I was going to purchase a week ago https://a.co/d/0gEcIKBN

I’m torn between trading it in or attempting to repair. I really enjoy my truck and have no interest in getting a new or used vehicle but realistically don’t want throw a bunch of money into something that will just happen again.

Thanks for any advice, tips or suggestions.

Here is some screenshots of my report.
Does any of this point to something kinda specific? It’s like reading in Russian to me, I don’t understand it.

Before you have cylinder heads pulled, I would have the mechanic pull a valve cover and inspect the cylinder #8 spark plug first, then possibly use a more advanced borescope to look inside the cylinder at the valves. Possibly perform a compression test and cylinder leakage test on the #8 cylinder.

A decent borescope can also go a long way to fully understanding what is going on by looking down at the cam and lifters as well as looking inside the cylinder(s). A decent borescope with with a thumb control to rotate and bend the camera around will allow the mechanic to look back up at the valves to make sure there is not a burner or chipped valve edge.

Something like this - https://www.amazon.com/Articulating-Detachable-Inspection-Semi-Rigid-Automotive/dp/B0G239JCXJ?th=1

Depending on what is found on the first inspection by removing the spark plug, the valve cover may need to be removed to inspect for bent pushrods, damaged rocker arms, and valve springs and make sure the #8 cylinder valves open all the way.

Unfortunately if the problem is with a lifter(s), a cylinder head does need to come off, if the cam is damage, both heads and the front of the engine need to come off which raises the cost and complexity.

^^^^^x2^^^^^

Pull #8 plug, inspect.
Do compression test.

Go from there.

I can’t seem to find if it’s worth fixing?
Yes it’s up to me but my concern is having a reputable shop repair a worst case scenario of all lifters and shaft only to have one of the new lifters give out pretty quickly.

Is the repair worth it in regards to eliminating the dreaded GM lifter issue for at least 100k miles?

I’m still waiting for proper diagnosis so I’m just trying to figure out repair vs trade in for a pickup truck.

West1 said:

I can’t seem to find if it’s worth fixing?
Yes it’s up to me but my concern is having a reputable shop repair a worst case scenario of all lifters and shaft only to have one of the new lifters give out pretty quickly.

Is the repair worth it in regards to eliminating the dreaded GM lifter issue for at least 100k miles?

I’m still waiting for proper diagnosis so I’m just trying to figure out repair vs trade in for a pickup truck.

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4 words Toyota 4runner Lexus GX460

I just sold my truck to carvana for next weeks pickup.

A buddy of mine who has been working on cars since a teen has offered to try and figure out what the problem is. Mentioned having to take the manifolds off and dive into the solenoid &/or lifters.

My question is, do I need to put the truck into service more or does disconnecting the battery override service more? He probably knows, this is just a question I have. Ty

You may have had a valve spring fail, that allows a valve to not close properly. 1 new spring and 1 hours labor could have your engine running like new again. Only way to check would be to pull the valve cover on that side and inspect. As already mentioned a compression check or better yet a leak down check will tell you which valve is leaking. The fact that you heard a bad noise and instantly the car ran bad is a pretty good clue.

PS: How did we end up with near identical forum names?

West 1 said:

You may have had a valve spring fail, that allows a valve to not close properly. 1 new spring and 1 hours labor could have your engine running like new again. Only way to check would be to pull the valve cover on that side and inspect. As already mentioned a compression check or better yet a leak down check will tell you which valve is leaking. The fact that you heard a bad noise and instantly the car ran bad is a pretty good clue.

PS: How did we end up with near identical forum names?

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Hopefully this video will upload.


As per username, that’s hilarious! I’ve used this username for quite some time now. The majority of forums I’m on, I use it. Back in roughly 2007 is when I first made the name on MFK (a freshwater fish forum) Lol.
That is pretty funny tho, I’ve never run across a similar username haha

West1 said:

I just sold my truck to carvana for next weeks pickup.

A buddy of mine who has been working on cars since a teen has offered to try and figure out what the problem is. Mentioned having to take the manifolds off and dive into the solenoid &/or lifters.

My question is, do I need to put the truck into service more or does disconnecting the battery override service more? He probably knows, this is just a question I have. Ty

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What did Carvana quote you for the Yukon (oops, Tahoe)? Was it near retail or more toward average trade in price. I've been thinking about selling our low mileage 2019 and curious about how these remote buyers work.

tom3 said:

What did Carvana quote you for the Yukon? Was it near retail or more toward average trade in price. I've been thinking about selling our low mileage 2019 and curious about how these remote buyers work.

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With the symptoms, 31,400

Funny that both names were allowed as is. I used West because my Father in law had just passed and he was West, I used West 1 because other names were already taken, just luck of the draw we ended up with such close names. HA

West 1 said:

Funny that both names were allowed as is. I used West because my Father in law had just passed and he was West, I used West 1 because other names were already taken, just luck of the draw we ended up with such close names. HA

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That's because your name has a space between West and the 1 and his does not it's all one word.