Engine judder, vibration or shaking: causes and affected cars

A juddering engine shakes, hesitates or jerks, at idle or when accelerating. The causes fall into two groups: an engine that runs badly (ignition, injection), or a drivetrain that passes on its vibrations (dual-mass flywheel, engine mounts, clutch). The engine warning light helps tell them apart: it mostly comes on in the first case.

An engine running badly: ignition and injection

When an injector leaks or a coil fails, the engine judders, the light comes on and the car can run on three cylinders (CarVerif, BMW 116i). Low-rev misfires are also reported on the BMW 220i (CarVerif). On diesels, injector wear shows as vibrations, hard starting and higher consumption, typically between 70,000 and 110,000 km on the Renault Laguna III 2.0 dCi (CarVerif); on the Audi A6 3.0 TDI, the unit injectors tire between 140,000 and 180,000 km (CarVerif).

A drivetrain that vibrates: flywheel, mounts, clutch

The dual-mass flywheel

It filters vibrations between the engine and the gearbox; as it deteriorates, it passes on jerks and ends up wearing the clutch, mounts and gear linkage (Fiches-auto, Audi Q5). On the Audi Q5 2.0 TDI 170, it becomes noisy from 80,000 km: cold vibrations, clunks, jerks when pulling away in first (CarVerif).

Engine mounts

Worn rubber engine mounts pass strong vibrations into the cabin; this is the recurring fault of the BMW 2 Series Gran Tourer (Auto & Moto Hebdo).

The clutch

A juddering clutch gives jerks when pulling away, often from cold (Fiches-auto, Audi Q2). See also slipping clutch and, on an automatic, automatic gearbox jerking.

Before buying a used car

Turn down a car that judders from cold, hesitates under light acceleration or jerks when manoeuvring (CarVerif, Audi Q3 II). A car that judders or has already run on three cylinders is not a good buy without a diagnosis (CarVerif, BMW 116i). Test it from cold, at idle, then accelerating at low revs.