Parts for your 1986 Mitsubishi Pajero-Oxygen sensor

1986 Mitsubishi Pajero oxygen sensor — is it actually fitted?

For Australian and New Zealand–delivered 1986 Mitsubishi Pajero models, an oxygen sensor (lambda sensor) generally isn’t fitted and isn’t part of normal servicing. Most local 1986 Pajeros ran either the 2.6-litre 4G54 carburetted petrol engine or the 2.3/2.5-litre turbo-diesel (4D55/4D56) with mechanical injection. These setups were engineered to meet period emissions without closed-loop feedback, so there’s no oxygen sensor in the exhaust on those vehicles.

Why no sensor? On the carburetted petrol 4G54, fuelling is managed mechanically by jets, needles and vacuum circuits. There’s no engine control unit adjusting mixtures based on exhaust oxygen, so an O2 sensor would have nothing to “talk to.” The diesels of the era run excess air (lean) by design and didn’t use catalytic converters or lambda control, so again, no need for a sensor. Typical emissions gear then included EGR, evaporative controls and air injection, all handled by vacuum and simple electronics rather than a closed-loop EFI system.

• 2.6L 4G54 (carburettor): No oxygen sensor on AU/NZ models.
• 2.3L/2.5L turbo-diesel (mechanical injection): No oxygen sensor.
• Market exception: Some North American “Montero” 2.6 models used a feedback carb with an O2 sensor and basic ECU to meet local regs.
• Later petrol EFI Pajeros (late first-gen/second-gen) introduced oxygen sensors alongside catalytic converters.

Technical references supporting this include the Mitsubishi Pajero/Montero Factory Service Manuals (mid-1980s editions) outlining carburettor and mechanical diesel control without lambda feedback, the Haynes Pajero/Montero manual (1983–1996) describing feedback-carb use in North America only, Mitsubishi ASA/EPC listings showing no AU/NZ O2 part call-outs for 1986 engines, and period ADR emissions requirements where carburetted/open-loop strategies remained common on local petrol models and diesels.

Bottom line for owners: unless the vehicle is an import with a feedback carb or a later EFI conversion, there’s no oxygen sensor to replace or maintain on a 1986 Pajero. Servicing should focus on carburettor tuning, vacuum hoses, EGR function, ignition timing and, for diesels, injector and pump health.

Popular questions

Does my 1986 Pajero have an oxygen sensor and how can I check?
Most AU/NZ 1986 Pajeros don’t. A quick check is to look for a sensor with wires screwed into the exhaust manifold or front pipe. If there’s nothing there and no wiring nearby, it’s likely not fitted. The under-bonnet emissions label and the engine/ECU wiring diagram (if any) are also good clues. Diesel models of that year won’t have one.

Can I retrofit an oxygen sensor to help tuning?
For factory systems, there’s nothing to connect it to on a carburetted or mechanically injected 1986 Pajero. However, tuners sometimes weld in a bung and use a temporary wideband O2 gauge to dial in mixtures on a carb rebuild or aftermarket EFI conversion. If you do, make sure placement and any emissions changes comply with local regulations.

Which Pajeros did start using oxygen sensors?
Petrol EFI variants introduced from the late 1980s onward (and subsequent generations) use oxygen sensors with catalytic converters. Diesels didn’t commonly use lambda sensors until much later when advanced aftertreatment systems appeared.