Chevrolet L61 (2.2 Ecotec)

The 2.2 Ecotec — GM's volume four of the 2000s, in the Cobalt, HHR, Ion, Vue, L-Series, Grand Am, Sunfire and Malibu. Its 2.4 sibling on the same architecture is the LAF / LE5.

It replaced two decades of pushrod fours with an all-aluminium, chain-driven, twin-cam engine, and the change of architecture is the thing to establish first: nothing about a GM 2.2 OHV of the previous decade transfers to it.

The timing chain is the wear item and it announces itself. The chain and its guides stretch, producing a rattle on start-up that settles as oil pressure comes up, and eventually camshaft-to-crankshaft correlation codes. Treat a start-up rattle on one of these as the chain rather than as ordinary noise for an old engine — it is a chain-driven design specifically so it would not need this at mileage, and at mileage it needs it.

It is port-injected, so the intake-valve carbon that dominates modern direct-injection diagnosis does not apply. A rough-running complaint here is ignition, fuel or the chain, not deposits — and these cars are numerous, cheap and often neglected, so basic service history is worth more than a guess.