LS lifter failure: causes and fixes
Common causes (any hydraulic-lifter LS):
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- Low oil level or pressure: the lifter doesn't pump up fully, leaves a gap and ticks. This is the most common cause.
- Worn or failing lifters.
- Aerated oil: from hard driving or an overfilled crankcase whipping air into the oil.
- Bent pushrods or damaged rockers.
AFM (Active Fuel Management) engines add their own failure mode: AFM uses oil-pressure-controlled lifters to deactivate cylinders. A failing AFM lifter can show up as a single-cylinder misfire, a persistent tick, a rough idle, low power and a cylinder-specific misfire code. It can progress to bent pushrods, a worn cam lobe and metal in the oil.
Fixes:
- Check and change the oil at the correct level and grade; that alone can quiet a marginal lifter.
- Pull the valve covers and look for bent pushrods or damaged rockers.
- Replace failed lifters before they wipe the cam or send debris through the engine.
- On AFM engines, a proper AFM delete means a non-AFM cam, all 16 lifters (not just the 8 AFM ones), new lifter trays, and blocking the AFM oil circuit. Plugging the passages while keeping AFM lifters is not a delete. The computer also has to be retuned. See the making power guide and tuning.