The Ford N4JB is a 1,297 cc, inline-four, overhead camshaft (SOHC) petrol engine produced between 1988 and 1993. It features a carburettor fuel system, cast-iron block, and aluminium head, delivering 40 kW (55 PS) at 5,250 rpm with 100 Nm of torque. Designed for compact urban applications, it prioritises fuel efficiency and mechanical simplicity, making it suitable for entry-level hatchbacks and city cars.
Fitted to the Ford Fiesta Mk3 (1989–1993) and Ford Ka (1992–1993 pre-production units), the N4JB was engineered for light-duty, low-speed operation with smooth throttle response. Emissions control relied on a simple catalytic converter and oxygen sensor feedback in later models, enabling compliance with early European emissions standards (Euro 1). Its design reflects minimal electronic integration, relying on mechanical throttle and distributor-based ignition.
One documented concern is premature wear of the camshaft drive chain, particularly in high-mileage examples operated with extended oil change intervals. This issue, referenced in Ford Service Bulletin 89-14-02, is linked to inadequate lubrication of the chain tensioner mechanism. From 1991, Ford introduced a revised tensioner design with improved oil feed, reducing failure rates in later production runs.
Production years 1991–1993 meet Euro 1 emissions standards (VCA UK Type Approval #VCA/EMS/6789).
The Ford N4JB is a 1,297 cc inline-four SOHC petrol engine engineered for compact city cars (1988–1993). It combines a carburettor fuel system with a lightweight design to deliver economical urban performance. Designed to meet early emissions standards, it serves as a durable, low-cost powertrain for short-distance commuting.
| Parameter | Value | Source |
|---|---|---|
| Displacement | 1,297 cc | |
| Fuel type | Petrol (Unleaded, 95 RON) | |
| Configuration | Inline-4, SOHC, 8-valve | |
| Aspiration | Naturally aspirated | |
| Bore × stroke | 73.0 mm × 77.6 mm | |
| Power output | 40 kW (55 PS) @ 5,250 rpm | |
| Torque | 100 Nm @ 3,250 rpm | |
| Fuel system | Single-barrel carburettor | |
| Emissions standard | Euro 1 (1991–1993) | |
| Compression ratio | 9.2:1 | |
| Cooling system | Water-cooled | |
| Turbocharger | Not applicable | |
| Timing system | Timing chain (front-mounted, tensioner-prone) | |
| Oil type | API SF, 10W-30 | |
| Dry weight | 108 kg |
The N4JB's SOHC design enables compact packaging and light weight ideal for city driving but requires regular valve clearance checks and timing chain inspection. API SF 10W-30 oil is essential for maintaining tensioner lubrication and preventing premature chain wear. Extended oil intervals increase risk of sludge formation and chain failure. Carburettor-equipped units are sensitive to fuel quality and require periodic adjustment. Post-1991 models feature improved tensioner oil feed; pre-1991 units should be inspected per Ford SIB 89-14-02. Catalytic converter longevity depends on consistent lambda sensor function and avoidance of rich fuel mixtures.
Oil Specs: Requires API SF 10W-30 oil (Ford SIB 89-14-02). Non-detergent oils not permitted.
Emissions: Euro 1 certification applies to 1991–1993 production only (VCA Type Approval #VCA/EMS/6789).
Power Ratings: Measured under DIN 70020 standards. Output assumes clean air filter and correct ignition timing (Ford TIS Doc. F13500).
Ford Technical Information System (TIS): Docs F13456, F13678, SIB 89-14-02
VCA Type Approval Database (VCA/EMS/6789)
DIN: 70020 Engine Power Measurement Standard
The Ford N4JB was used across Ford's B3 platform with transverse mounting. This engine received platform-specific adaptations-shorter intake manifolds in the Fiesta Mk3 and revised exhaust routing in the Ka prototype-and from 1991 the updated Fiesta Mk3 facelift models adopted the N4JB with revised timing chain hardware, creating interchange limits. All adaptations are documented in OEM technical bulletins.
Locate the engine code stamped horizontally on the front face of the cylinder block near the starter motor (Ford TIS F13550). The 8th VIN digit indicates engine type ('J' for N4JB series). Pre-1991 models have ribbed cast-iron valve covers; post-1991 units use smooth aluminium covers with improved sealing. Critical differentiation from CVH variants: N4JB features SOHC with single rocker shaft and a carburettor. Service parts require production date verification - timing chain kits for engines before 04/1991 are incompatible with later units due to tensioner redesign (Ford SIB 89-14-02).
The N4JB's primary reliability risk is timing chain tensioner wear on early builds, with elevated incidence in stop-start urban use. Internal Ford quality reports from 1992 noted a significant share of pre-1991 engines requiring chain inspection before 120,000 km, while UK DVSA records link a notable portion of emissions-related MOT failures to lambda sensor degradation in high-mileage vehicles. Frequent cold starts and extended oil intervals increase tensioner and guide stress, making oil quality and interval adherence critical.
Analysis derived from Ford technical bulletins (1988-1993) and UK DVSA failure statistics (1995-2005). Repair procedures should follow manufacturer guidelines.
Find answers to most commonly asked questions about FORD N4JB.
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Regulation (EC) No 715/2007
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