Renault B4D / H4D (1.0 SCe / TCe)

Renault's three-cylinder petrol engines — the naturally aspirated 1.0 SCe and the turbocharged 0.9 and 1.0 TCe — fitted to the Clio, Twingo, Captur, Sandero and Micra, and the entry powertrain across the alliance's small cars.

They are small, chain-driven and built to a price, and their diagnostic profile reflects that: the complaints that recur are ignition coils, the crankshaft position sensor, and carbon around the throttle body producing an unstable idle. No systemic internal failure defines them in the way one defines the 1.2 TCe four that sat above them.

The turbocharged versions bring the usual dependence on oil condition and, on the direct-injected variants, intake-valve deposits at mileage. Because these cars sell heavily into markets with variable fuel quality and long service intervals, fuel and oil history explain more faults here than the odometer does.