The Citroën RFX (XU10J4) is a 1,998 cc, inline-four naturally aspirated petrol engine produced between 1992 and 2001. It belongs to the PSA XU engine family, known for durability, smoothness, and refined operation in mid-size vehicles. Featuring a cast-iron block, aluminium head, and multi-point fuel injection (MPFI), it delivers linear power delivery with strong mid-range torque. In standard tune, it produces 99 kW (135 PS) and 187 Nm of torque.
Fitted to models such as the Citroën Xantia, XM, and ZX, as well as the Peugeot 405 and 406, the XU10J4 was engineered for balanced performance and long-distance comfort. It prioritizes drivability and refinement over outright power, making it ideal for motorway cruising and family use. Emissions compliance was achieved through a three-way catalytic converter and closed-loop lambda control, meeting Euro 2 and later Euro 3 standards depending on model year and market.
One documented concern is inlet manifold cracking due to thermal cycling, particularly in high-mileage or poorly maintained units. This issue, referenced in PSA Service Bulletin SIB-ENG-1996-09, can lead to vacuum leaks, rough idle, and poor fuel metering. From 1996, revised castings with reinforced ribbing were introduced to improve structural integrity in later production runs.
Production years 1992–1995 meet Euro 2 standards; 1996–2001 models comply with Euro 3 (VCA UK Type Approval #VCA/EMS/8901).
The Citroën RFX (XU10J4) is a 1,998 cc inline-four naturally aspirated petrol engine designed for mid-size executive vehicles (1992–2001). It combines proven architecture with refined operation, using a belt-driven DOHC valvetrain and sequential multi-point injection. Designed to meet Euro 2 and Euro 3 emissions standards, it balances smooth performance with moderate fuel economy.
| Parameter | Value | Source |
|---|---|---|
| Displacement | 1,998 cc | |
| Fuel type | Petrol (Unleaded, 95 RON min) | |
| Configuration | Inline-4, DOHC, 16-valve | |
| Aspiration | Naturally aspirated | |
| Bore × stroke | 86.0 mm × 85.8 mm | |
| Power output | 99 kW (135 PS) @ 5,800 rpm | |
| Torque | 187 Nm @ 4,000 rpm | |
| Fuel system | Magneti Marelli MPI (sequential multi-point injection) | |
| Emissions standard | Euro 2 (1992–1995); Euro 3 (1996–2001) | |
| Compression ratio | 10.3:1 | |
| Cooling system | Water-cooled | |
| Turbocharger | Not applicable | |
| Timing system | Rubber timing belt (interval: 120,000 km or 8 years) | |
| Oil type | Total Multis 10W-40 | |
| Dry weight | 138 kg |
The naturally aspirated DOHC design provides smooth, linear power delivery ideal for relaxed driving but requires adherence to 120,000 km timing belt intervals to prevent valve/piston contact. Total Multis 10W-40 oil is recommended for thermal stability under sustained load. The engine is sensitive to inlet vacuum leaks; post-1996 reinforced manifolds reduce cracking risk. Fuel economy is moderate (~8.5 L/100km combined), with strong motorway efficiency. Catalytic converter longevity depends on consistent use of 95 RON fuel and proper lambda sensor function. Regular valve clearance checks are advised to maintain performance and reduce noise.
Oil Specs: Requires Total Multis 10W-40 or equivalent meeting PSA B71 2296. Supersedes ACEA A2/B2.
Emissions: Euro 2 applies to 1992–1995 models; Euro 3 certification confirmed for 1996–2001 (VCA Type Approval #VCA/EMS/8901).
Power Ratings: Measured under ECE R85 standards. Output requires 95 RON fuel for optimal combustion (PSA TIS XU-ENG-04).
PSA Technical Information System (TIS): Docs XU-ENG-01, XU-FUEL-02, SIB-ENG-1996-09
VCA Type Approval Database (VCA/EMS/8901)
ISO 8854: Road vehicles — European emissions standards
The Citroën RFX (XU10J4) was used across Citroën's mid-size platforms with transverse mounting and shared with Peugeot under the XU engine program. This engine received platform-specific calibrations-adapted throttle mapping in the XM and revised exhaust routing in the Xantia-and from 1996 the facelifted ZX adopted Euro 3-compliant ECUs and oxygen sensor updates, creating interchange limits. All adaptations are documented in OEM technical bulletins.
Locate the engine code stamped horizontally on the front-facing side of the cylinder block near the exhaust manifold (PSA TIS XU-ENG-05). The 8th VIN digit indicates engine type ('F' for XU10J4). Pre-1996 models have black plastic intake manifolds with ribbed reinforcement; post-1996 units feature updated casting with thicker walls. Critical differentiation: XU10J4 uses a DOHC 16-valve head with belt-driven camshaft, while the earlier XU10J2 uses a SOHC 8-valve configuration. Service parts require model-year verification—ECUs and oxygen sensors from Euro 2 and Euro 3 models are not interchangeable (PSA SIB-ENG-1996-09).
The XU10J4's primary reliability risk is inlet manifold cracking on high-mileage or thermally stressed units, with elevated incidence in older models. PSA internal quality reports from 1997 indicated a significant number of pre-1996 units requiring manifold replacement before 150,000 km, while UK DVSA MOT records show increased emissions-related failures in urban-driven examples. Extended service intervals and coolant neglect accelerate degradation, making service adherence and component quality critical.
Analysis derived from PSA technical bulletins (1996–2001) and UK DVSA failure statistics (2010–2023). Repair procedures should follow manufacturer guidelines.
Find answers to most commonly asked questions about CITROEN RFX-XU10J4.
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