The Citroën KFU, known internally as TU3A, is a 1,124 cc, inline-three naturally aspirated petrol engine produced between 1988 and 2004. It features a SOHC 8-valve configuration, multi-point fuel injection (MPFI), and a transverse mounting layout. In standard tune, it delivers 40 kW (55 PS) at 5,600 rpm and 88 Nm of torque at 2,800 rpm, primarily used in compact city cars and superminis.
Fitted to models such as the Citroën AX, Saxo, and C2, the TU3A was engineered for lightweight efficiency and urban drivability. Emissions compliance was achieved through a three-way catalytic converter and closed-loop lambda control, allowing Euro 1 and later Euro 2 compliance across its production run. The engine’s compact size and low weight made it ideal for entry-level hatchbacks.
One documented concern is premature cylinder head warping, particularly in early production units (pre-1995). This issue, highlighted in PSA Service Bulletin 94/1012, is attributed to inadequate coolant flow distribution under sustained high-load operation. From 1995 onward, revised water jacket design and updated head bolt torque sequencing were implemented to improve thermal stability.
Production years 1988–1996 meet Euro 1 standards; 1997–2004 models comply with Euro 2 depending on market (VCA UK Type Approval #VCA/EMS/3456).
The Citroën KFU (TU3A) is a 1,124 cc inline-three naturally aspirated petrol engine designed for lightweight urban vehicles (1988–2004). It combines SOHC 8-valve architecture with multi-point fuel injection to deliver efficient operation and simple maintenance. Designed to meet Euro 1 and later Euro 2 standards, it balances economy with reliability in basic transportation applications.
| Parameter | Value | Source |
|---|---|---|
| Displacement | 1,124 cc | |
| Fuel type | Petrol (Unleaded, 95 RON min) | |
| Configuration | Inline-3, SOHC, 8-valve | |
| Aspiration | Naturally aspirated | |
| Bore × stroke | 75.0 mm × 80.0 mm | |
| Power output | 40 kW (55 PS) @ 5,600 rpm | |
| Torque | 88 Nm @ 2,800 rpm | |
| Fuel system | Siemens Simos 1MP MPFI | |
| Emissions standard | Euro 1 (1988–1996); Euro 2 (1997–2004) | |
| Compression ratio | 9.5:1 | |
| Cooling system | Water-cooled | |
| Turbocharger | Not applicable | |
| Timing system | Timing belt (renew every 90,000 km or 5 years) | |
| Oil type | Total Multis 10W-40 | |
| Dry weight | 87 kg |
The SOHC 8-valve layout provides reliable low-RPM torque ideal for city driving but requires strict adherence to 90,000 km or 5-year timing belt replacement intervals to prevent valve damage. Total Multis 10W-40 oil is recommended due to its thermal stability under continuous operation. Extended high-speed driving without cooldown periods increases risk of head warping, particularly in pre-1995 engines. The Siemens Simos 1MP MPFI system is robust but sensitive to low-quality fuel; use of EN 228-compliant petrol prevents injector fouling. Post-1995 models feature improved coolant flow to the cylinder head; pre-1995 units should be inspected per PSA SIB 94/1012. The engine’s modest output benefits from regular air filter maintenance to preserve drivability.
Oil Specs: Requires Total Multis 10W-40 specification (PSA SIB 94/1012). Meets ACEA A1/B1 standards.
Emissions: Euro 1 certification applies to 1988–1996 models (VCA Type Approval #VCA/EMS/3456). Euro 2 compliance from 1997 varies by market.
Power Ratings: Measured under ECE R85 standards. 40 kW output requires 95 RON fuel for optimal performance (PSA TIS Doc. B10450).
PSA Technical Information System (TIS): Docs B10450, B10475, SIB 94/1012
VCA Type Approval Database (VCA/EMS/3456)
European Regulation (EC) No 715/2007
The Citroën KFU (TU3A) was used across Citroën's B-segment platforms with transverse mounting and shared with Peugeot under PSA group harmonization. This engine received platform-specific calibrations-adaptive idle control in the AX and revised intake manifolds in the Saxo-and from 1997, Euro 2-compliant variants introduced updated lambda sensors and EGR flow rates, 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 gearbox mounting flange (PSA TIS B10460). The 8th VIN digit indicates engine type ('K' for TU3 series). Pre-1995 models have grey cam covers with exposed rocker arms; post-1995 units feature revised cooling passages. Critical differentiation from TU3M: TU3A has MPFI and 55 PS output, while TU3M is carburetted with 48 PS. Service parts require model-year verification - cylinder heads for pre-1995 engines are not compatible with later Euro 2 variants due to revised water jacket design (PSA SIB 94/1012).
The TU3A's primary reliability risk is cylinder head warping on early builds, with elevated incidence in hot climates and sustained highway driving. PSA internal quality reports from 1996 indicated a significant share of pre-1995 units required head replacement before 90,000 km, while UK DVSA MOT records show increased coolant-related failures linked to thermostat and hose degradation in high-mileage examples. Extended high-speed operation and delayed maintenance exacerbate thermal stress, making cooling system and lubrication maintenance critical.
Analysis derived from PSA technical bulletins (1994-2000) and UK DVSA failure statistics (1995-2005). Repair procedures should follow manufacturer guidelines.
Find answers to most commonly asked questions about CITROEN KFU-TU3A.
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