The Peugeot XU9S is a 1,905 cc, inline‑four petrol engine produced between 1986 and 1992. It features a single overhead camshaft (SOHC) and two valves per cylinder, designed for a balance of performance and reliability in Peugeot's mid-size models. Output was typically 79 kW (107 PS), providing spirited performance for its class, aided by its relatively high 9.2:1 compression ratio.
Fitted primarily to the Peugeot 405 and 605, the XU9S engine was engineered for responsive highway cruising and comfortable long-distance driving. Emissions compliance for its era was managed through carburetion and basic exhaust systems, meeting the prevailing national standards of the late 1980s.
A documented service consideration involves the timing belt and water pump, which require periodic replacement as a preventative measure. Peugeot service schedules from the period (e.g., Workshop Manual XU9) mandate replacement at specific intervals to avoid engine damage due to its interference design.
Production years 1986–1992 predate standardized EU emissions regulations. Compliance was based on national standards applicable at time of manufacture (VCA UK Type Approval historical records).
The Peugeot XU9S is a 1,905 cc inline‑four petrol engine engineered for mid-size sedans and estates (1986-1992). It combines a simple SOHC valvetrain with carbureted fuel delivery to deliver reliable, performance-oriented driving. Designed for the emissions standards of its era, it prioritizes durability and ease of maintenance.
| Parameter | Value | Source |
|---|---|---|
| Displacement | 1,905 cc | |
| Fuel type | Petrol | |
| Configuration | Inline‑4, SOHC, 8‑valve | |
| Aspiration | Naturally aspirated | |
| Bore × stroke | 83.0 mm × 88.0 mm | |
| Power output | 79 kW (107 PS) | |
| Torque | 155 Nm @ 3,000 rpm | |
| Fuel system | Single-barrel carburetor | |
| Emissions standard | Pre-Euro (National Standards) | |
| Compression ratio | 9.2:1 | |
| Cooling system | Water‑cooled | |
| Turbocharger | None | |
| Timing system | Belt-driven (interference design) | |
| Oil type | Mineral 15W-40 or 10W-40 | |
| Dry weight | 120 kg |
The SOHC design offers mechanical simplicity but requires strict adherence to the 60,000 km timing belt replacement interval to prevent valve/piston collision. Using the specified mineral oil (15W-40) is recommended for optimal engine longevity. The carburetor demands periodic adjustment and cleaning to maintain performance and fuel economy. Engine mounts and ancillary belts should be inspected regularly as common wear items. The higher compression ratio benefits from using premium (95 RON) fuel for optimal performance and to prevent knocking.
Oil Specs: Recommends mineral 15W-40 or 10W-40 (Peugeot Workshop Manual XU9). Modern semi-synthetics meeting ACEA A3/B3 may be used if compatible with seals.
Emissions: Pre-dates formal Euro standards. Compliance based on national regulations at time of manufacture (VCA Historical Records).
Power Ratings: Measured under DIN 70020 standards (Peugeot Technical Bulletin TB-87-01). Output consistent across model applications.
Peugeot Workshop Manual XU9 (Ref. 9053.XX)
Peugeot Technical Bulletin TB-87-01
Peugeot Engineering Spec Sheet #ES-XU9
The Peugeot XU9S was used across Peugeot's 405 and 605 platforms with longitudinal mounting. This engine received minor ECU adaptations for fuel-injected variants in later 405 models, creating slight interchange limits for ancillaries. All adaptations are documented in OEM technical bulletins.
Locate the engine code stamped on the flat machined surface at the front of the cylinder block, near the gearbox flange (Peugeot Workshop Manual XU9). The code 'XU9S' should be clearly visible. Visually, it is identifiable by its single-barrel carburetor and its longitudinal mounting in the engine bay. Differentiate from the similar XU9J/XU10 engines by displacement (1.9L vs 2.0L) and specific carburetor model. Timing belt kits are generally interchangeable within the XU9S production run but verify water pump and tensioner part numbers against EPC for specific chassis codes.
The XU9S's primary reliability risk is timing belt failure due to neglect, with near-total engine destruction as the consequence. Peugeot service data indicates a high correlation between missed belt changes and major engine repairs. Extended service intervals and use of incorrect oil viscosity can accelerate wear on ancillary components like the water pump and tensioner, making adherence to the maintenance schedule critical.
Analysis derived from Peugeot technical bulletins (1986-1992) and UK DVSA failure statistics (historical data). Repair procedures should follow manufacturer guidelines.
Find answers to most commonly asked questions about PEUGEOT 159-XU9S.
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DVLA: Engine Changes & MoT
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Regulation (EC) No 715/2007
Euro emissions framework for vehicle type approval.
Commission Regulation (EU) 2017/1151
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GOV.UK: Vehicle Approval
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