Parts for your 1987 Mitsubishi Pajero-Spark plugs

1987 Mitsubishi Pajero spark plugs: what they do, which engines use them, and when to replace

Whether spark plugs are relevant on a 1987 Mitsubishi Pajero depends on the engine. Technical references such as the Mitsubishi factory workshop manual for first‑gen Pajero/Montero (1983–1991) and the Haynes Repair Manual confirm that the petrol engines (2.6L 4G54 and 3.0L V6 6G72) use spark plugs, while the diesel engines (2.3/2.5L 4D55/4D56) do not. Diesel ignition is compression‑based, supported by glow plugs for cold starts, as outlined in standard texts like the Bosch Automotive Handbook and Mitsubishi diesel service literature.

For diesel 1987 Pajero models, spark plugs are not used because diesel fuel self‑ignites under high compression, instead, they run glow plugs to aid starting when cold. That’s normal diesel design and not a fault—there’s simply no spark ignition system fitted on those variants.

For petrol‑powered 1987 Pajero models, spark plugs are the tiny workhorses that fire the air‑fuel mix under the bonnet thousands of times a minute. Good plugs help the old bus start cleanly, idle smoothly, pull hard under load, and sip less petrol. Over time, electrodes wear, gaps open up, and deposits build—so performance and economy tail off, and misfires can creep in. The factory workshop manual and plug makers’ catalogues specify the correct heat range and gap for each engine, sticking to those specs is key.

As part of routine servicing, it pays to:

• Inspect plugs at service intervals and replace on condition. Older copper‑core plugs are often due around 20,000–30,000 km, long‑life platinum/iridium options can stretch much further, sometimes 60,000–100,000 km. Always defer to the Pajero’s owner’s or workshop manual and the plug manufacturer’s guidance.
• Check and set the gap only if the plug type allows it. Many modern fine‑wire plugs come pre‑gapped—handle gently to avoid damaging the tip.
• Use the correct socket and a torque wrench. Tighten to the torque specified by the plug maker or workshop manual. Over‑tightening can strip aluminium threads, under‑tightening can cause blow‑by.
• Avoid anti‑seize unless the plug manufacturer explicitly calls for it, it can alter torque values. A dab of dielectric grease on the boot helps future removal and resists moisture.
• Replace tired leads or coil boots that show cracks, burn marks, or high resistance, and keep the distributor cap/rotor (where fitted) in good nick to prevent cross‑fire.

Signs it’s time to look at the plugs include hard starting, a rough idle, sluggish performance under load, pinging, or worse fuel economy than usual. Fresh, correctly gapped plugs and healthy ignition components can make a noticeable difference to how a 1987 Pajero drives, whether it’s towing, touring, or tackling bush tracks.

Popular questions about 1987 Mitsubishi Pajero spark plugs

Which 1987 Pajero engines actually use spark plugs?
Petrol engines do: the 2.6‑litre 4G54 and the 3.0‑litre V6 6G72. The diesel 2.3/2.5‑litre 4D55/4D56 variants don’t use spark plugs, they use glow plugs to aid cold starts and rely on compression ignition for running.

How often should spark plugs be replaced on a 1987 Pajero petrol model?
Service life depends on plug type and driving conditions. As a rule of thumb, copper plugs can be due around 20,000–30,000 km, while platinum/iridium types can run much longer. Always follow the Mitsubishi workshop manual and the plug manufacturer’s interval and heat‑range guidance.

What spark plug type and gap should be used?
Use the heat range and part numbers specified for the exact engine, and set the gap to the spec in the owner’s/workshop manual or on the under‑bonnet sticker. Many fine‑wire plugs are pre‑gapped—handle with care and avoid forcing the ground strap.