2004 Proton Impian 1.6L Petrol · YN54 GGV

The 1.6-litre 16V Mitsubishi 4G18 engine employs a wasted-spark ignition system featuring two coil packs mounted directly above cylinders two and four, with high-tension (HT) leads feeding cylinders one and three. Radiant cylinder head heat and minor oil seepage from the rocker cover gasket break down the dielectric silicone insulation on the coil pack extension tubes and lead boots. High voltage arcs across the spark plug recess to the engine block rather than firing the plug. This produces noticeable engine misfiring under load, hesitation when accelerating in higher gears, a flashing check engine light, and potential catalytic converter damage from unburnt fuel.

The Proton Impian's standout chassis dynamics were achieved via an independent multi-link rear suspension setup engineered in partnership with Lotus. However, the system relies on numerous rubber trailing arm bushings and spherical rose joints that suffer severe wear from UK pothole strikes and corrosive road salt. Over time, the rubber degrades, tears, and debonds from its outer steel sleeves. This allows excessive rear-wheel toe and camber deflection, resulting in rear-end instability and wandering at motorway speeds, clunking sounds over road imperfections, uneven inner rear tyre tread wear, and MOT failure.

The hydraulic power steering system on the Impian routes rigid steel hydraulic pipes across the lower front crossmember and steering rack body. In the wet British climate, road grit and salt spray thrown from the front wheels accumulate in the retaining brackets and strip the pipe coating. Severe rust pitting develops along the pipe walls, eventually causing pressurized power steering fluid to seep or spray out under pump load. In addition to creating heavy steering assistance drop-out during parking and pump whine, leaking fluid contaminates front suspension bushes and results in an MOT refusal.