Mercedes-Benz M271 (1.6 and 1.8)

The four-cylinder petrol behind the Kompressor badge — a belt-driven supercharger rather than a turbocharger, which is the distinction the badge is actually stating and the reason its failure modes look nothing like a turbo engine's. Later CGI members replaced the supercharger with direct injection and turbocharging.

Its signature fault is the timing chain and, more specifically, the balance-shaft gear on the earlier version. The gear wears prematurely, timing drifts, and the engine sets camshaft-crankshaft correlation codes; left alone it ends in a chain jump. It is the single most consequential thing to check on a high-mileage M271, and the repair is an engine-out job on many installations.

The supercharger's own clutch and the intake manifold's swirl-flap mechanism are the other two recurring items, and both produce a loss of power without necessarily storing a component-specific code.

⚑ Supercharged early, turbocharged later, at 1.6 and 1.8 litres. That change matters more than the displacement: the Kompressor cars and the CGI cars share a designation and not a failure pattern, and the timing chain reputation belongs to the later ones.