2009 Toyota IQ 1.0L Petrol · D4 REU

Urban-driven 1.0-litre three-cylinder models suffer from heavy soot and carbon buildup within the exhaust gas recirculation (EGR) valve and intake manifold channels. Persistent short urban trips prevent the engine from reaching self-cleaning temperatures, causing the valve pintle to stick open. This introduces unmetered exhaust gas into the intake charge at low rpm, causing rough hunting idle, jerking under light throttle, and unexpected engine stalling when stopping at junctions.

Early 2009–2010 models can develop an intermittent knocking sensation or sudden temporary loss of power steering assistance. The electronic power steering ECU control logic was overly sensitive to voltage interference from the alternator when navigating sharp bumps, causing the control module to disconnect steering motor assistance and illuminate the P/S warning lamp. Toyota issued UK safety recall R/2010/181 to reflash the EPS ECU software.

The optional Multidrive continuously variable transmission (CVT) can develop a noticeable shudder and hesitation when setting off from a standstill, particularly on upward gradients. The fault stems from degraded CVT fluid, contaminated solenoid valves within the hydraulic valve body, or slippage of the steel drive belt across the variable pulleys due to missed fluid changes.