فرسودگی پولی ضربه‌گیر میل‌لنگ

The harmonic damper on the crankshaft nose, worn so its rubber bonding has failed. It is two masses bonded by rubber and exists to absorb crankshaft torsional vibration — it is not simply a pulley.

When the bond fails the outer ring moves relative to the hub, so anything timed from marks on that ring is wrong, and the vibration it was absorbing is passed into the engine. Where a sensor reads from the damper the timing signal itself wanders, which produces misfire and correlation codes with a healthy sensor. Look for the outer ring out of line with the hub, or a wobble as the engine idles. The vibration it stops damages the crankshaft over time, so this is worth acting on rather than living with.