Isuzu 4ZE1

Isuzu's 2.6 petrol four — in the Trooper and the Rodeo.

It is a large, slow-turning, iron-block four built for torque in vehicles that spend their time towing or off the road, and its reputation is for surviving rather than for performing.

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

The timing belt is an interference design and, on vehicles this old and this often used commercially, the history is almost never documented.

The 4ZD1 2.3 beside it is the same design one size down and its results apply; the 6VD1 V6 that replaced both is a different engine with its own page here.

Parts supply is the practical constraint, not the engine — it is usually what decides whether one of these is worth repairing.