Mercedes-Benz W203 misfires and rough running
Mercedes-Benz W203 petrol engine: what causes misfires?
Most often a faulty ignition coil, spark plugs or leads. Other causes are a leaking vacuum hose or breather hose, the fuel pump or a clogged fuel filter. Fault code P0301 means misfires in cylinder 1, P0302 in cylinder 2 and so on.
Mercedes-Benz W203: how do you identify a faulty ignition coil?
Swap the coil of the misfiring cylinder with the coil of another cylinder. If the fault moves with it, the coil is faulty. Sometimes the fault shows only at high revs or under load, and swapping does not reveal it. A cheap new coil can be defective, so use a quality brand.
Mercedes-Benz M271: what can cause rough running and a warning light?
On the M271 a typical cause is an intake air leak: the vacuum hoses of the supercharger and intake manifold and the breather hose under the air filter become brittle and crack. The timing chain can also stretch and jump, which throws the ignition off. Read the fault codes before replacing parts.