Chevrolet 122 (Family II)

GM's overhead-cam four of the 1980s and 1990s — the 122, or Family II — in the S-10 and Sonoma at 1.9 and 2.0 litres.

⚑ It is not the pushrod 2.2 beside it in the same trucks, and that is the distinction worth establishing first: LN2 is an overhead-VALVE design with a timing chain, and this is an overhead-CAM design with a timing belt. They share a showroom, a displacement class and nothing else — including whether a snapped belt destroys the engine.

The belt is the item that ends these. It is an interference design and, on cars this old, the history is almost always unknown.

Its running complaints are pre-modern and physical. Vacuum leaks, a tired idle air control and a failing coolant temperature sensor account for most of them, and the few codes it sets are general enough that testing beats reading them.

It is the ancestor of the Ecotec, which replaced it and shares its bore spacing — but nothing else transfers, and Ecotec advice applied here is wrong about the belt, the head and the management.