3.5 EcoBoost cam phaser rattle: the cold-start knock, Ford's revised phasers, and what the fix costs outside warranty

A two-second knock on cold start that sounds like a diesel is the second-generation 3.5 EcoBoost's cam phasers. Ford revised them and issued a customer satisfaction program.

The 2017-and-newer 3.5 EcoBoost uses camshaft phasers that lock at rest so the chain does not slap the phaser on start-up. The original lock pins wore, the phasers unlocked, and the chain rattled the phaser for a couple of seconds until oil pressure built.