2017 Smart (mcc) Forfour 0.9L Petrol · LE17 CTF

A 2017 Smart Forfour with two consecutive pass certificates (the most recent on 27 July 2026 and the prior on 31 July 2025) presents a generally favourable roadworthiness picture, yet the failure recorded on 19 October 2024 reveals mechanical vulnerabilities that warrant close scrutiny. That test was failed outright due to an emissions reading exceeding the manufacturer's CO limit after the second fast idle, compounded by a tester being unable to complete the emissions check owing to a rattling timing chain. These are not trivial items on the 1.0-litre or 0.9-litre turbocharged three-cylinder units fitted to this generation, as a noisy timing chain suggests chain stretch and tensioner wear, while elevated CO can indicate mixture issues, a tired lambda sensor, or ignition-related faults. Two further Major defects were recorded at the same test for perished anti-roll bar linkage ball joint dust covers on both front sides, allowing dirt ingress and accelerating joint wear. The intervening clean tests demonstrate that the emissions and chain issues were addressed, but a buyer must establish the quality and scope of that repair work rather than assume a permanent fix. Against an age of roughly nine years, the recorded mileage of 94,069 equates to an average annual accumulation of approximately 10,452 miles, which is broadly typical for a city-focused Forfour and indicates consistent rather than sporadic use. There are no prolonged gaps in the testing record, suggesting the vehicle has remained in regular service throughout its life on the road, which is mechanically beneficial for components such as the timing chain, turbo seals, and braking system that suffer from extended standing. The relatively high absolute mileage for a small Smart, however, places meaningful wear on the clutch, rear axle assembly, suspension bushes, and exhaust mounting hardware, all of which are common failure points on higher-mileage examples of this platform. The presence of a tyre screw advisory in October 2023 (repaired prior to retest) is an isolated incident rather than evidence of poor wheel or tyre management. With the anti-roll bar linkage ball joints having been flagged on the front axle, particular attention should be paid on any test drive to clonking or rattling noises transmitted through the front end when traversing speed bumps, kerbs, or uneven tarmac. Steering response should be checked for vagueness or a shimmy under braking, as worn drop links and perished bushes can compromise body control and introduce uneven tyre wear across the front pair. The timing chain rattle, although reportedly resolved by the 2025 test, demands a cold-start inspection: listen for a metallic rattle from the right-hand side of the engine for the first few seconds after ignition, which would indicate residual tensioner weakness. A scan for stored fault codes relating to the camshaft or crankshaft correlation would confirm whether the chain has been correctly re-timed or merely silenced. The recorded oil leak advisory, although classed as not excessive, should not be dismissed on a turbocharged three-cylinder engine, where seepage from the cam cover, turbo oil feed, or lower sump area is common and tends to worsen with mileage. During inspection, look for fresh oil residue on the engine block, undertray, and around the turbocharger housing, and check the underside of the bonnet for staining. Given the emissions failure history, verify that a recent service has been documented with fresh spark plugs and a clean air filter element, and confirm the condition of the lambda sensor and catalytic converter heat shield. Finally, the rear suspension on the Forfour uses a de Dion-style beam that is sensitive to bush deterioration, so push down firmly on each rear corner and release, watching for any delayed rebound, knocking, or instability that would indicate worn trailing arm or beam bushes requiring replacement.