Lifters

[21TahoeDisappoint]

I beg to differ on the view that it is faulty parts. If that were the case, GM would have announced a recall. They would know the supplier of the faulty parts, the shipment lot of the faulty parts, and the vehicle manufacture date of the vehicles with the faulty parts. The fact that there isn't a recall speaks volumes. This is a design flaw. This is very common. My 2021 Tahoe High Country experienced this at 7,400 miles. The dealer was very familiar with the issue. I had the Christmas Tree of warning lights before the issue became apparent, which I suspect was due to cylinder misfire before the bent rods and springs got so bad that the engine started knocking and shaking.

In my view, the fact that GM will only replace the impacted cylinder bank at this time means that its only a matter of time before the issue happens again. There are many posts on social media and the Chevy/Yukon etc. message boards. To me it sounds like an oil pressure/cylinder deactivation design problem.

Why is GM being so silent on this? Probably because there is no solution yet, and the magnitude of the problem in terms of financial and reputational impact is significant.

 

[Quark]

You bought a first year complete redesign model in which a narrow run of VINs have some faulty parts in their engine. Your 3 4-Runners were all the same and the design hadn't changed in a long long time, apples to oranges comparison.

Once your engine is replaced, the vehicle will continue to be fantastic and will offer a level of luxury and performance that a 4-Runner isn't even designed to compete with.

Please excuse and correct me if I'm wrong, the broken valve springs were attributed to a limited run of faulty parts but the collapsed lifter/bent push rods failure is an ongoing problem and has been reported regularly by truck owners for years.

 

[Quark]

Every manufacturer is working to cut costs. The good ones have been doing it since the beginning of time and that's why they're still around. The fact that dealers are replacing these lifters with fixed parts tells me the supplier produced a bad batch.

You are stating the obvious that manufacturers are continually cutting costs. One other thing that keeps manufacturers in business is quality and continual improvement however if you look at American dependability rates we aren't doing it right.

If GM were dealing with a bad batch of potentially faulty lifters then why aren't they replacing all the lifters in an engine that had one fail? GM's lifter problem goes back years they know the failure rate and they gamble that these engines had a failure and the other lifters should be fine. The lifters aren't designed correctly or can't be manufactured to consistently perform as they are intended.

 

[swathdiver]

Please excuse and correct me if I'm wrong, the broken valve springs were attributed to a limited run of faulty parts but the collapsed lifter/bent push rods failure is an ongoing problem and has been reported regularly by truck owners for years.

In the Gen IV engines, there were three generations of AFM lifters which improved their function under various conditions. The number one cause of lifter failure though was not the lifters themselves but of VLOM failure. The solenoids in the VLOM either failing or getting out of time which caused the lifters to collapse or activate at the wrong time which in turn bent the pushrods and often worse. You're right and I was wrong, the limited run of faulty parts does indeed cover the valve springs and not the lifters.

AFM became very reliable after about 2011 and the GEN V motors even more so. But now the DFM engines it seems are having some growing pains, again, new technology (2019+).

 

[Quark]

In the Gen IV engines, there were three generations of AFM lifters which improved their function under various conditions. The number one cause of lifter failure though was not the lifters themselves but of VLOM failure. The solenoids in the VLOM either failing or getting out of time which caused the lifters to collapse or activate at the wrong time which in turn bent the pushrods and often worse. You're right and I was wrong, the limited run of faulty parts does indeed cover the valve springs and not the lifters.

AFM became very reliable after about 2011 and the GEN V motors even more so. But now the DFM engines it seems are having some growing pains, again, new technology (2019+).

I can tell you are more knowledgeable about this than I am. My 2012 has not had a problem and knowing this was corrected I can quit worrying.

One thing is certain, I won't be replacing my Ol' Hoe till they figure this out.

 

[jayoco]

You are stating the obvious that manufacturers are continually cutting costs. One other thing that keeps manufacturers in business is quality and continual improvement however if you look at American dependability rates we aren't doing it right.

If GM were dealing with a bad batch of potentially faulty lifters then why aren't they replacing all the lifters in an engine that had one fail? GM's lifter problem goes back years they know the failure rate and they gamble that these engines had a failure and the other lifters should be fine. The lifters aren't designed correctly or can't be manufactured to consistently perform as they are intended.

No, that's not what I'm inferring. I think you should read the OP and and then my response.

 

[Quark]

No, that's not what I'm inferring. I think you should read the OP and and then my response.

You didn't infer anything you stated, "The fact that dealers are replacing these lifters with fixed parts tells me the supplier produced a bad batch."

It is not a "bad batch".

 

[Stbentoak]

Regardless of “bad batches” where is the suppliers quality control?

I’d be lying if I said I never made a bad part in my business (Aerospace), but they never left my plant to go to any major engine supplier. If they did….people could die. I took that very seriously as a supplier and business owner. What if you were in the hospital and your ventilator had a bad “lifter” ? Bad quality put businesses like mine out of business in a matter of months if it got out into the world…..

 

[Quark]

Regardless of “bad batches” where is the suppliers quality control?

I’d be lying if I said I never made a bad part in my business (Aerospace), but they never left my plant to go to any major engine supplier. If they did….people could die. I took that very seriously as a supplier and business owner. What if you were in the hospital and your ventilator had a bad “lifter” ? Bad quality put businesses like mine out of business in a matter of months if it got out into the world…..

I'm currently going with the hypothesis that it's a failure of design. The PCM sends a signal to the high oil pressure solenoid to switch the lifter off and on at prescisly the right time. The problem might be programming, PCM fault, solenoid delay, oil pressure issue, or a vast array of assembly errors or parts nonconformity. The primary concern in designing the drivetrain is to comply with government mandates secondary is performance. What could go wrong with that?

 

[jayoco]

You didn't infer anything you stated, "The fact that dealers are replacing these lifters with fixed parts tells me the supplier produced a bad batch."

It is not a "bad batch".

Okey dokey.