Sold my new tahoe

[swathdiver]

Not just warranty repairs. At about 110k miles I broke a valve spring. The dealers techs found the spring right away. When they told me they found a broken spring, I asked what the game plan was and he said, “we will replace the spring.” I said, “why not replace them all?”, he said, “why?”. I said, “because I am paying for it.” He said, “right, will do!”

They're trained or conditioned to replace just that broken piece generally speaking. We had a bad input clutch piston go in a transmission (4T65) and that's all they fixed when it was torn down and put back together (under warranty).

 

[wsteele]

They're trained or conditioned to replace just that broken piece generally speaking. We had a bad input clutch piston go in a transmission (4T65) and that's all they fixed when it was torn down and put back together (under warranty).

I think it takes a TSB, recall or some other kind of “program” before everything that might be suspect is changed. Mine had new pistons and rings installed largely on GMs nickel under the AFM oil consumption TSB.

 

[Quark]

Look folks, the Gen IV engines when AFM was re-introduced (since the 80s) also had teething problems. GM redesigned the lifters twice and made some other improvements. The biggest enemy for those early engines was dirty oil. They were also specified to run a blend of conventional and synthetic oil and that didn't help either. Even then, hundreds of thousands remained perfectly reliable. These forums are where we come to gripe and solve problems mostly, not to say, "My truck runs great today and didn't need to do anything to it but add gas."

I reckon what's killing the DFM lifters is the programming being out of time, I cannot even begin to fathom the programming required to cycle 1 to 6 cylinders off and on within milliseconds so that the lifters don't get wrecked.

I would posit that the programming isn't out of time but the execution of that programming isn't within spec when they fail. The complexity of the design demands exact execution amid a myriad of variables such as oil and gas quality, operating temperature, individual engine component tolerances, interaction among other component controllers and driving conditions not to mention driver input.

Refinement may be possible but it will require analyzing specific combinations of events preceding failure that have so far been either unexpected or extremely difficult to overcome within budget. And that budget is being reduced as money is diverted to electric vehicle development to comply with government mandates. In light of that how hard will GM try to ensure future faith in their gas engine technology when present sales levels are sufficient to fund the next thing.

 

[OR VietVet]

Since I will likely be in the ground by the time the government makes our decision for us and tells us we can only buy new vehicles that are electric but also start to force the gas engine/diesel engine rigs off the road, I may consider buying a second NBS rig to make sure I have one if I can't get parts for a broken one.

 

[Bill 1960]

Considering the precise timing events required for ignition timing control, gasoline direct injection, etc. I don’t see control of a valve actuator as a technical challenge with regard to timing the event. The computers in modern cars are extremely fast, and precision real-time control is what they do.

Modern diesels will open and close the injector multiple times in a single power stroke. That’s why they don’t clatter any more like the older ones with all the fuel input in a single shot.

My money would be on a metallurgy or machining QC issue.

 

[Quark]

Considering the precise timing events required for ignition timing control, gasoline direct injection, etc. I don’t see control of a valve actuator as a technical challenge with regard to timing the event. The computers in modern cars are extremely fast, and precision real-time control is what they do.

Modern diesels will open and close the injector multiple times in a single power stroke. That’s why they don’t clatter any more like the older ones with all the fuel input in a single shot.

My money would be on a metallurgy or machining QC issue.

That would imply the problem is easy. If it were easy why haven't they solved it?

 

[Bill 1960]

That would imply the problem is easy. If it were easy why haven't they solved it?

How do you know they haven’t solved it?

 

[Quark]

How do you know they haven’t solved it?

An assumption based on empirical evidence, the evidence provided by posters that are having problems. That assumption will be proven right or wrong in a few months. The problem appeared with the introduction of DFM in 2019 which doesn't support a bad batch of whatever component one wishes to blame.

Correction: Problem first appeared with the introduction of AFM, the technology has been problematic from the beginning. Why on earth would we attribute failures to a bad batch of something.

 

[Just Fishing]

Majority of the issues i have researched out are all related to the extended oil changes that the manf recommends.
that's for my wife's Buick with the 3.6l as well.

When the engine on my tahoe failed, i was astounded by how bad the carbon build up was.
Years and years of extended oil changes (nearly 180k).
Finally that's what did it in
sludge released, plugged the filter, bypassed, then took out the first bearing in the oil path.
The rear cam bearing!
Also resulted in low oil pressure due to a stuck bypass in the oil pump, the final nail.

IMO,
Just change your oil, use quality name brand stuff, and don't cheap out on filters.
Also don't believe this extended oil change nonsense.

 

[OR VietVet]

When running shops I told many many many customers that oil is the blood of the engine and if you don't take care of it by using quality oil and filter and timely intervals, mileage or time, they can kiss the engine goodbye. Even with full synthetic oil and premium Wix filter, I do it every 5k miles or 6 months, whichever is first. I live where I work and have owned this rig for a year in July and only put 2k miles on it. Still has had 2 oil changes.