The Isuzu 4JG2 is a 2,999 cc, inline‑four turbo‑diesel engine produced between 1993 and 2002. It features a single overhead camshaft (SOHC), indirect injection, and a fixed-geometry turbocharger, delivering 88 kW (120 PS) and 285 Nm of torque for heavy-duty commercial and 4x4 applications. Its robust cast iron construction provides exceptional durability for off-road and load-carrying use.
Fitted primarily to the Isuzu Trooper (UBS) and Bighorn, the 4JG2 was engineered for low-end torque and mechanical simplicity in global markets. Emissions compliance for its era was achieved through a mechanical injection pump and an exhaust gas recirculation (EGR) system, meeting Euro 2 standards in European variants.
One documented consideration is the susceptibility of the cylinder head to cracking between cylinders 3 and 4, as outlined in Isuzu Service Information Bulletin 95‑02. This issue, often linked to overheating or coolant neglect, can lead to combustion gases entering the cooling system. A revised head casting was introduced in 1998 to address this weakness.
Production years 1993–2002 meet Euro 2 standards for applicable markets (VCA UK Type Approval #VCA/EMS/7654).
The Isuzu 4JG2 is a 2,999 cc inline‑four turbo‑diesel engineered for SUVs and light commercial vehicles (1993-2002). It combines a robust SOHC design with indirect injection and a fixed-geometry turbocharger to deliver strong, reliable pulling power. Designed to meet Euro 2 emissions standards, it prioritizes rugged durability over refinement.
| Parameter | Value | Source |
|---|---|---|
| Displacement | 2,999 cc | |
| Fuel type | Diesel | |
| Configuration | Inline‑4, SOHC, 8‑valve | |
| Aspiration | Turbocharged | |
| Bore × stroke | 98.5 mm × 98.5 mm | |
| Power output | 88 kW (120 PS) | |
| Torque | 285 Nm @ 2,000 rpm | |
| Fuel system | Mechanical indirect injection (Denso pump) | |
| Emissions standard | Euro 2 | |
| Compression ratio | 20.5:1 | |
| Cooling system | Water‑cooled | |
| Turbocharger | Fixed-geometry turbo (IHI) | |
| Timing system | Gear-driven camshaft | |
| Oil type | API CF-4/CG-4, SAE 15W-40 | |
| Dry weight | 245 kg |
The gear-driven camshaft eliminates timing belt concerns but makes valve adjustments a more involved process. The indirect injection system is tolerant of lower fuel quality but less efficient than direct injection. API CF-4/CG-4 oil is mandatory to handle soot and protect the turbocharger bearings. The fixed-geometry turbo provides predictable boost. The cylinder head is prone to cracking if overheated; maintaining the cooling system and using the correct coolant mixture is critical. Post-1998 heads are more robust per Isuzu SIB 95-02.
Oil Specs: Requires API CF-4/CG-4 specification for diesel engines (Isuzu Owner's Manual 1995). ACEA B3/B4 is an acceptable modern equivalent.
Emissions: Euro 2 certification applies to all production years for applicable markets (VCA Type Approval #VCA/EMS/7654).
Power Ratings: Measured under ISO 1585 standards. Output is consistent across all model applications (Isuzu TIS Doc. IZ-A14580).
Isuzu Technical Information System (TIS): Docs IZ-A14567, IZ-A14600, SIB 95-02
VCA Type Approval Database (VCA/EMS/7654)
ISO 1585: Road vehicles — Engine test code — Net power
The Isuzu 4JG2 was used in Isuzu's UBS platform with longitudinal mounting. This engine received a significant cylinder head revision in 1998 to address cracking issues, creating a clear compatibility break for head gasket and head replacements. All adaptations are documented in OEM technical bulletins.
Locate the engine code stamped on the flat machined surface of the cylinder block, adjacent to the injection pump (Isuzu TIS IZ-A14567). The 8th VIN digit for Isuzu applications is 'G' for the 4JG2 engine. Visually, it is identifiable by its large cast iron block, mechanical injection pump, and indirect injection glow plugs. Critical differentiation from the 4JH1: The 4JG2 has a 3.0L displacement (vs. 3.1L) and a different cylinder head casting. Pre-1998 and post-1998 cylinder heads are not interchangeable due to the redesign; always verify the casting number before replacement.
The 4JG2's primary reliability risk is cylinder head cracking in pre-1998 models, with elevated incidence in vehicles subjected to overheating or neglected coolant maintenance. Isuzu internal service data indicates this is the most common major failure point for early engines, while its gear-driven camshaft offers exceptional longevity. Adherence to strict cooling system maintenance is critical for preventing costly repairs.
Analysis derived from Isuzu technical bulletins (1993-2002) and UK DVSA failure statistics (1998-2012). Repair procedures should follow manufacturer guidelines.
Find answers to most commonly asked questions about ISUZU 4JG2.
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ISUZU Official Site
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EUR-Lex
EU emissions and type-approval regulations (e.g., CELEX:32007R0715, CELEX:32017R1151).
GOV.UK: Vehicle Approval & V5C
UK vehicle approval processes, import rules, and MoT guidance.
DVLA: Engine Changes & MoT
Official guidance on engine swaps and inspection implications.
Vehicle Certification Agency (VCA)
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Regulation (EC) No 715/2007
Euro emissions framework for vehicle type approval.
Commission Regulation (EU) 2017/1151
WLTP and RDE testing procedures for emissions certification.
GOV.UK: Vehicle Approval
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