Parts for your 1990 Mitsubishi Pajero-Knock sensor

1990 Mitsubishi Pajero – Knock Sensor: Fitted or Not?

Based on Mitsubishi’s Factory Service Manual for Pajero/Montero (1989–1991, Engine Electrical and Fuel Systems) and the Mitsubishi ASA electronic parts catalogue, a knock sensor is fitted to 1990 Pajeros with the 3.0‑litre 6G72 V6 EFI (commonly listed as MD133911/MD141510 in parts references). The same factory literature, plus Gregory’s Pajero 1983–1996 Service and Repair Manual, shows no knock sensor provision on the 2.6‑litre 4G54 (carburetted) or the 2.5‑litre 4D56 diesel engines.

For V6 models where a knock sensor is present, it’s a small piezoelectric microphone that “listens” for detonation and lets the ECU trim ignition timing to keep the engine safe and efficient. On the 6G72, it’s mounted in the V of the block under the intake plenum with a single‑wire lead into the engine loom. If it fails or the wiring goes brittle, the ECU may pull timing as a safeguard, leaving the Pajero feeling flat, sluggish up hills, and heavier on fuel. In some cases the ECU’s diagnostic procedure (OBD‑I flash codes) will flag a knock sensor fault.

Servicing the 1990 V6 knock sensor is mostly about prevention and careful replacement. Heat and age are the big enemies, so during major intake work it’s smart to inspect the sensor and its sub‑loom for cracking or oil contamination. When replacing, stick with a quality sensor that matches the factory spec, ensure the mating surface on the block is clean and dry, and tighten it to the workshop manual torque—over‑ or under‑tightening can make it deaf or overly sensitive. Don’t use sealants on the face, and route the lead away from ignition leads to avoid electrical noise. After fitting, clear any stored codes, run the correct RON for local fuel, and road‑test under load to confirm the ECU isn’t still pulling timing.

If the Pajero in question is a 4G54 petrol or 4D56 diesel, a knock sensor isn’t used. The 2.6‑litre carb model relies on a conventional distributor with vacuum/mechanical advance and has no ECU strategy for knock control, which is why Mitsubishi didn’t provision a sensor in the loom or the block. The 2.5‑litre diesel of that era is mechanically governed and doesn’t employ a spark‑ignition knock sensor, combustion characteristics and control systems are different, so there’s no factory knock sensor in the diesel harness or manuals.

• Technical sources referenced: Mitsubishi Pajero/Montero Factory Service Manual (1989–1991), Mitsubishi ASA parts catalogue (6G72 KS listings MD133911/MD141510), Gregory’s Pajero 1983–1996 manual (ignition/diesel sections).

FAQs

Does a 1990 Pajero have a knock sensor?
It depends on the engine. The 3.0‑litre 6G72 V6 EFI has a knock sensor. The 2.6‑litre 4G54 petrol (carb) and 2.5‑litre 4D56 diesel do not.

Where is the knock sensor on the 3.0 V6, and how hard is it to change?
It’s in the valley of the V6 block beneath the intake plenum. Replacement typically requires removing the upper intake components, so allow time and use the correct torque on refit to avoid false readings.

What symptoms point to a faulty knock sensor on the V6?
Sluggish performance, poor fuel economy, pinging under load, and an ECU fault code are common signs. The ECU may retard timing to protect the engine, which feels like a lack of power.