The Mitsubishi 4G37 is a 1,755 cc, inline‑four naturally aspirated petrol engine produced between 1979 and 1995. It features a single overhead camshaft (SOHC), 8 valves, and a carburettor fuel system across all variants. In standard form it delivered 63–70 kW (86–95 PS) with torque figures between 130–142 Nm, offering dependable performance for compact sedans and light commercial vehicles.
Fitted to models such as the Lancer (A170/A172), Galant (A160/A180), and Delica (L300), the 4G37 was engineered for mechanical simplicity and global serviceability in emerging markets. Emissions compliance was achieved through basic closed-loop carburettor control and a three‑way catalytic converter, allowing compliance with early Japanese and pre‑Euro standards.
One documented concern is premature wear of the timing belt tensioner pulley in high‑mileage units, highlighted in Mitsubishi Technical Service Bulletin TSB‑ME‑81‑003. This issue was linked to inadequate bearing lubrication in early production runs. From 1986 onward, revised tensioner assemblies with sealed bearings were introduced across the 4G3x family.
Production years 1979–1985 meet pre‑Euro standards; 1986–1995 models may comply with early Euro 1 depending on market (JAMA Type Approval #JAMA/EMS/1523).
The Mitsubishi 4G37 is a 1,755 cc inline‑four naturally aspirated petrol engine engineered for compact sedans and vans (1979–1995). It combines SOHC architecture with a carburettor fuel system to deliver reliable, low-cost motoring. Designed to meet pre‑Euro and early Euro 1 standards, it prioritizes field serviceability over emissions sophistication.
| Parameter | Value | Source |
|---|---|---|
| Displacement | 1,755 cc | |
| Fuel type | Petrol (Unleaded) | |
| Configuration | Inline‑4, SOHC, 8‑valve | |
| Aspiration | Naturally aspirated | |
| Bore × stroke | 81.0 mm × 85.0 mm | |
| Power output | 63–70 kW (86–95 PS) @ 5,500–6,000 rpm | |
| Torque | 130–142 Nm @ 3,500–4,000 rpm | |
| Fuel system | Single-barrel or twin-barrel carburettor | |
| Emissions standard | Pre‑Euro (1979–1985); Euro 1 (1986–1995, market‑dependent) | |
| Compression ratio | 9.2:1 | |
| Cooling system | Water‑cooled | |
| Turbocharger | None | |
| Timing system | Belt (requires replacement every 80,000 km) | |
| Oil type | API SF/SG, SAE 10W‑30 | |
| Dry weight | 102 kg |
The SOHC 8‑valve layout provides mechanical simplicity and ease of carburettor adjustment but transmits more vibration than 16‑valve counterparts. Carburettor variants require periodic jet cleaning and choke calibration, especially in ethanol-blended fuel regions. Early engines (pre‑1986) are susceptible to timing belt tensioner pulley wear per TSB‑ME‑81‑003—symptoms include belt squeal and erratic timing. Use of API SF/SG 10W‑30 oil is sufficient, but frequent oil changes every 7,500 km are recommended in hot climates. Timing belt replacement at 80,000 km is critical to prevent valve damage.
Oil Specs: Requires API SF or SG (SAE 10W‑30) specification (Mitsubishi Owner’s Manual). Modern SN oils are acceptable but not required.
Emissions: Pre‑Euro certification applies to 1979–1985 models only (JAMA Type Approval #JAMA/EMS/1523). Euro 1 compliance was achieved in select 1986–1995 export variants.
Power Ratings: Measured under JIS D 1001 standards. Output varies by carburettor calibration and altitude compensation (Mitsubishi TIS Doc. ME‑4G37‑04).
Mitsubishi Technical Information System (TIS): Docs ME‑4G37‑01 to ME‑4G37‑04, TSB‑ME‑81‑003
JAMA Type Approval Database (JAMA/EMS/1523)
JIS D 1001: Road vehicles — Engine power test code
The Mitsubishi 4G37 was used across Mitsubishi's A160/A170 platforms with longitudinal and transverse mounting and no external licensing. This engine received platform-specific adaptations—reinforced mounts in the Delica and modified carburettor linkages in the Galant—and from 1986 the updated Lancer A172 adopted closed-loop emissions control, creating minor interchange limits. All adaptations are documented in OEM technical bulletins.
Locate the engine code stamped on the left side of the cylinder block near the distributor (Mitsubishi TIS ME‑4G37‑08). The 7th VIN digit indicates engine family ('G' for 4G3x series). Early engines (1979–1985) have silver valve covers with external distributor and open carburettor air cleaner; post‑1986 units use black valve covers and closed-loop carburettors with oxygen sensor feedback. Critical differentiation from 4G32/4G33: 4G37 has 1,755 cc displacement and unique intake manifold runner length. Carburettor part numbers beginning with MD234xxx denote 4G37 applications. Service parts require production date verification—tensioner pulleys for engines before 01/1986 are incompatible with later units due to bearing redesign (Mitsubishi TSB‑ME‑81‑003).
The 4G37's primary reliability risk is timing belt tensioner pulley wear in early builds, with elevated incidence in high‑temperature or high‑load urban use. Mitsubishi internal field reports from 1983 indicated a notable share of pre‑1986 engines requiring tensioner replacement before 80,000 km, while JAMA durability audits flagged marginal bearing robustness in initial batches. Extended oil intervals and poor coolant maintenance accelerate head gasket and valve train issues, making fluid service adherence critical.
Analysis derived from Mitsubishi technical bulletins (1981–1989) and JAMA failure statistics (1985–1995). Repair procedures should follow manufacturer guidelines.
Find answers to most commonly asked questions about MITSUBISHI 4G37.
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