N43B20

Rough cold idle, slow throttle response, misfires, gradual loss of low-end response. Direct injection puts no fuel over the intake valves, so crankcase vapour deposits bake on undisturbed.

Check: Not visible without a borescope. Treat it as a service item that's due unless there's a receipt. It's not a fault, it's an unbudgeted maintenance cost.

Rattle for one to three seconds on cold start, worst after the car has stood overnight. The hydraulic tensioner bleeds down. Caught early it's a tensioner; ignored it becomes chain and guides.

Check: The car must be stone cold. Stand outside it at start-up and listen for a rattle from the front of the engine.

Engine warning light, noticeably worse fuel consumption, loss of lean-burn mode. The NOx sensor in the exhaust degrades. The engine then runs permanently rich, which is drivable but expensive.

Check: Scan for NOx sensor and lean-mode codes. Ask the seller what the car returns on a run. A lean-burn four that drinks like a six has a dead sensor.

Rough idle, shaking at standstill, misfire warnings, poor cold running, sometimes limp mode. The stratified-charge petrol engines use piezo injectors that are sensitive to fuel quality and wear out. They typically fail one at a time over several years.

Check: Scan for per-cylinder misfires and check how many injectors have already been replaced. A car with all six done recently is worth a real premium over one with none.