Before you buy a used Renault Clio (IV).

Look out for: Metallic chain rattle, especially when cold or at idle; engine light with a crankshaft–camshaft correlation code; in serious cases the chain jumps and damages the valves.

Ask them to check: With any chain noise or a P0016 code, diagnose straight away: measure the stretch and check the tensioner and guides before the timing jumps. Shorten oil-change intervals.

Look out for: Oil needs topping up often; the level can reach the minimum with no warning on the dashboard. In advanced cases, timing noise, loss of power or serious engine damage.

Ask them to check: Measure oil consumption with the dipstick over several thousand km, ask the dealer for a diagnosis and the calibration update, and keep every maintenance invoice to request support.

Look out for: Particulate-filter or emissions warning, limp mode with loss of power and frequent regenerations.

Ask them to check: Read the soot load with a diagnostic tool, run a forced regeneration at the garage and check the differential-pressure sensors and EGR. Make long road trips now and then.

Look out for: Uneven idle, jerks when accelerating, lack of power or the engine going into limp mode, sometimes with the engine warning light on.

Ask them to check: At the workshop: read the codes with diagnostic equipment (EOBD P0400 to P0404 or P0172; Renault DF077, DF084 or DF241), test the valve electrically and its opening with the engine warm, and find where the oil comes from (breather, turbo, level). Pierburg advises against cleaning it, as it can be damaged: it is replaced if faulty, and an engine ECU update sometimes solves it.

Look out for: After a visit to the dealer, flat spots when accelerating and judder at steady speeds; sometimes higher diesel consumption. On the Mégane IV and Kadjar the engine may start and then stall.

Ask them to check: Ask a Renault or Dacia dealer for the new injection ECU reprogramming for these symptoms (Dacia has offered it since May 2024 and Renault since January 2025). It is not a recall with a letter: you have to ask for it. First have them rule out other causes (particulate filter, boost pressure sensor).

Look out for: Low-speed judder, harsh 1st–2nd shifts, clunks when selecting D or R, overheating warnings in traffic and a “Check auto gearbox” message.

Ask them to check: Check software updates and the gearbox oil-change history; reset the clutch adaptations with a diagnostic tool and replace the clutch only if wear exceeds the adjustment range.

Look out for: Hard to start or will not start, stalls, loses power or jerks; sometimes air bubbles show in the clear fuel pipe.

Ask them to check: At the workshop, in this order: look for air and leaks in the low-pressure circuit and prime it; check the fuel filter bowl for metal swarf (if there is any, the whole injection system is replaced); measure the rail pressure, the IMV regulator's resistance (4.8–5.8 Ω) and each injector's return flow (25 ml at most in the test). A new injector's code must be written into the ECU.