How a Failing N47 / N57 Injector Presents
On the N47 / N57, a failing 0445110478 injector typically presents first as a single-cylinder ticking knock at warm idle — louder than the same fault on the later B47 because the N47 ran a slightly lower rail pressure and the failed unit's mistimed shot is more audible against the background combustion. The second is a long-crank cold-start episode that lasts ten to fifteen seconds — the rail loses prime overnight while a worn injector seat bleeds fuel into one cylinder. The third is a measurable loss of fuel economy combined with shrinking DPF regen intervals — typical of late-stage nozzle wear.
Because the N47/N57 platform also has the well-known timing-chain rear-end failure mode, workshops sometimes misattribute injector knock to imminent chain failure. The two faults sound alike to an untrained ear. Run the leak-off test first — a single injector returning visibly more than its siblings is the unit to replace, and the chain stretch is a separate (and serious) job.
