Peugeot TU

PSA's long-running small petrol four, in 1.1, 1.4 and 1.6 litre forms — the engine of the 106, 205, 206, Saxo, C2, C3 and, in licence-built form, of the Iran Khodro and other locally assembled cars that make it one of the most numerous engines in several markets outside Europe.

It is a simple belt-driven, port-injected design with no variable timing on most versions, and its diagnostics are correspondingly old-fashioned: vacuum leaks, a worn idle control valve, a failing coolant temperature sensor and tired ignition components account for the large majority of running complaints. Codes are few and general, so physical testing matters more here than scan data.

The timing belt is the maintenance item that ends engines, and on cars of this age history is usually unknown. In markets with poor fuel quality, carbon in the head and on the valves is a routine finding rather than a fault, and it responds to cleaning.

⚑ PSA stopped building it and Iran Khodro did not. The TU5 is still made under licence in Tehran, where it powers the Runna, the Pars and the Tara — the last of those launched in 2020, four years after the family ended in Europe. So a TU5 in front of you may be newer than any European parts catalogue expects, and the Iranian-built version is designated TU5P.