Driving in L9 and DFM

jimgeb said:

Is there is any evidence to indicate that disabling DFM electronically will prevent lifter failure,
since the collapsible lifters still remain?

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It does not PREVENT failure, but it does delay / put off the failure further into the future.
If you intend to keep it, this could give you time til a full delete becomes plausible / feasible.
Or you COULD pass it off to the next owner (along with the disablement of course).

Marky Dissod said:

It does not PREVENT failure, but it does delay / put off the failure further into the future.
If you intend to keep it, this could give you time til a full delete becomes plausible / feasible.
Or you COULD pass it off to the next owner (along with the disablement of course).

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The actual de-act mechanism of the lifter failing is really rare with the DFM engines outside of the known bad batch. Like really really really rare. I've only seen a couple that I remember in the last couple of years. The roller bearings are what can fail and cause cam damage and that can happen to any hydraulic roller lifter. Lifters spinning in the bore can happen but usually involves abuse from my experience but same deal it doesn't matter that the lifter is a de-act variant. The hydraulic lash adjusting mechanism could in theory fail but they usually just tick until they pump up.


The main reason to not run in DFM is the vibration/buzzing some people notice. Especially once the exhaust valve torsion spring gets lazy and the valve doesn't dampen out the NVH.

RG23RST said:

Lifters spinning in the bore can happen but usually involves abuse from my experience but same deal it doesn't matter that the lifter is a de-act variant.

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Curious, what would you see or define as "abuse?"

Fless said:

Curious, what would you see or define as "abuse?"

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When the customer can’t provide oil change records and the engine clearly wasn’t maintained with the correct oil and mileage. Yes some people do run cheap recycled oil in their $65K vehicles and expect warranty coverage.

Thats 1 out of a thousand reasons I’m getting out of dealer work and going to work for the county in their fleet shop.

@RG23RST Does the dfm vibration cause other damage such as trans problems? Mine definitely feels rough when dfm is active and its only at 5k miles.