Volvo B3154T5

The 1.5 turbocharged three-cylinder developed by Volvo and Geely together — in the XC40 and, as a plug-in hybrid, in the Geely Coolray.

It is a VEA engine with a cylinder removed, sharing bore spacing and much of its architecture with the 2.0 four, which is the useful thing to carry into a diagnosis: VEA results usually apply, and four-cylinder assumptions about smoothness do not.

A three-cylinder is not inherently balanced. It carries a balance shaft and it vibrates at idle in a way the four does not. An owner reporting shake at a stop is very often describing normal behaviour, and establishing that first saves chasing mounts.

In the plug-in cars it drives a hybrid system, so a complaint about power delivery, response or charging belongs there rather than to the engine — and the high-voltage precautions those cars need are absent from the petrol ones wearing the same engine.

It is direct-injected and turbocharged, so intake-valve carbon at mileage and a turbocharger whose life tracks oil condition are both expected rather than exceptional.