Honda L13 (L-series, 1.2–1.4)

Honda's 1.3-litre four — the entry engine of the Jazz and Fit, and in i-DSI form one of the more unusual designs in this catalogue: two spark plugs per cylinder, fired at slightly different times, to burn a lean mixture completely in a compact chamber.

That matters when diagnosing a misfire, because an i-DSI engine has twice the ignition components of an equivalent four and a single failed plug or coil produces a partial misfire rather than a dead cylinder — a softer symptom that is easy to attribute elsewhere. Later i-VTEC versions returned to a single plug per cylinder.

The hybrid variants pair this engine with Honda's IMA system, which changes what a starting or charging complaint means entirely. Mechanically the family is durable, and its recurring findings are valve clearances drifting out of specification at high mileage — a genuine scheduled task on Honda engines of this era, and a common cause of a tick or a misfire that no sensor explains.