The Citroën KAY (TU3A) is a 1,124 cc, inline — three naturally aspirated petrol engine produced between 1988 and 2005. It forms part of the PSA TU engine family, known for compact dimensions, simplicity, and reliability in small urban vehicles. Featuring a cast — iron block, aluminium head, and single overhead camshaft (SOHC), it delivers modest power with excellent fuel economy. In standard tune, it produces 40 kW (55 PS) and 86 Nm of torque.
Fitted to entry — level models su…
Production years 1988–1992 meet Euro 1; 1993–1999 models comply with Euro 2; 2000–2005 units meet Euro 3 standards (VCA UK Type Approval #VCA/EMS/7890).
The Citroën KAY (TU3A) is a 1,124 cc inline-three naturally aspirated petrol engine designed for lightweight urban vehicles (1988–2005). It combines compact packaging with proven reliability, using a timing belt-driven SOHC valvetrain and multi-point fuel injection. Designed to meet Euro 1 to Euro 3 emissions standards, it prioritizes economy and ease of servicing over performance.
| Parameter | Value | Source |
|---|---|---|
Displacement | 1,124 cc | |
Fuel type | Petrol (Unleaded, 95 RON min) | |
Configuration | Inline-3, SOHC, 6-valve | |
Aspiration | Naturally aspirated | |
Bore × stroke | 75.0 mm × 84.8 mm | |
Power output | 40 kW (55 PS) @ 5,800 rpm | |
Torque | 86 Nm @ 3,000 rpm | |
Fuel system | Magneti Marelli multi-point fuel injection (MPFI) | |
Emissions standard | Euro 1 (1988–1992); Euro 2 (1993–1999); Euro 3 (2000–2005) | |
Compression ratio | 9.7:1 | |
Cooling system | Water-cooled | |
Turbocharger | Not applicable | |
Timing system | Rubber timing belt (interval: 60,000 km or 4 years) | |
Oil type | Total Multis 10W-40 | |
Dry weight | 85 kg |
The Citroën KAY (TU3A) was used across Citroën's A-segment platforms with transverse mounting and shared with Peugeot under the TU engine program. This engine received platform-specific calibrations-adapted idle control in the AX and revised exhaust routing in the Saxo-and from 2000 the facelifted C1 adopted Euro 3-compliant ECUs and oxygen sensor updates, creating interchange limits. All adaptations are documented in OEM technical bulletins.
Engine Finders UK Ltd, which operates EngineCode.uk, can pass your enquiry to engine suppliers in the UK. The service is for vehicles in the United Kingdom, with UK delivery or fitting. This is a commercially connected service, and sending an enquiry does not confirm diagnosis or compatibility.
Diagnostic reminder: If a technician has recommended replacing the engine, you can send an enquiry to engine suppliers in the UK. Confirm the diagnosis first: an engine-code record does not diagnose a fault.
The TU3A's primary reliability risk is cylinder head warping on high-mileage or poorly maintained units, with elevated incidence in thermally stressed engines. PSA internal quality reports from 2001 indicated a notable number of pre-2000 models requiring head resurfacing before 100,000 km, while UK DVSA MOT records show increased emissions-related failures in urban-driven examples. Extended service intervals and coolant neglect accelerate thermal degradation, making service adherence and system integrity critical.
Analysis derived from PSA technical bulletins (1998–2005) and UK DVSA failure statistics (2010–2023). Repair procedures should follow manufacturer guidelines.
The most common questions about engine codes, what they mean, how to find them and how this database works
The TU3A is generally reliable when maintained properly. Its simple design and proven architecture make it durable, but critical attention must be paid to the 60,000 km timing belt interval and cooling system maintenance. Cylinder head warping is common on older units, especially pre-2000 models. With timely servicing and use of correct oil (10W-40), these engines regularly exceed 120,000 km.
The most documented issues are cylinder head warping due to overheating, timing belt failure from missed services, and idle control valve clogging. These are addressed in PSA service bulletins, particularly SIB-ENG-1998-04 and SIB-ENG-2000-06. Coolant leaks from plastic housings are also seen in high-mileage urban examples.
The TU3A was used in the Citroën AX (1.1), C1 (1.1i), and Saxo (1.1) from 1988 to 2005. It was also shared with Peugeot (106 1.1, 206 1.1) under the TU engine family. All applications are front-wheel drive with transverse engine mounting.
The TU3A has very limited tuning potential due to its 6-valve SOHC design and low displacement. Mild carburettor upgrades or ECU remaps yield minimal gains (+3–5 kW). Performance modifications are rare; most owners focus on reliability. Aftermarket exhausts or air filters offer slight improvements but are not cost-effective for most users.
In combined driving, expect 4.8–5.5 L/100 km (51–60 mpg UK). Real-world consumption is excellent in city driving (~4.5 L/100km), but motorway efficiency drops to ~6.5 L/100km (43 mpg UK). Fuel injection helps consistency, but driving style significantly impacts economy.
Yes. The TU3A is an interference engine. If the timing belt fails or jumps, piston-to-valve contact will occur, causing catastrophic internal damage. Given the 60,000 km service interval, proactive replacement of the belt, tensioner, and water pump is essential to avoid expensive repairs.
PSA specifies Total Multis 10W-40 (or equivalent meeting PSA B71 2296). This mineral-based oil is suitable for the engine's thermal demands. Oil must be changed every 15,000 km or annually to maintain lubrication and prevent sludge buildup, especially in stop-start driving.
Comprehensive technical documentation and regulatory references
EngineCode.uk is operated by Engine Finders UK Ltd. It provides engine-reference information and an optional commercial enquiry service. It is not an official manufacturer website. Check the record's sources and confirm vehicle-specific details before relying on it for parts, repairs or replacement.
Our editorial standard prioritises relevant manufacturer documentation and official regulatory sources. The sources and verification status for a record should be checked alongside the data.
A statement is not verified merely because a source is listed. Where supporting evidence is missing or conflicting, the record should identify that limitation. Please report unsupported or inconsistent information.
Transparency in gaps
A missing or unverified value does not mean the manufacturer has withheld it. We distinguish information not yet verified, information not available to us, and information explicitly not disclosed by the source.
Regulatory Stability
EU regulations are referenced using CELEX identifiers for long-term stability.
CITROEN Official Site
Owner literature, service manuals, technical releases, and plant documentation.
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)
UK type-approval authority for automotive products.
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
UK compliance and certification requirements for imported and modified vehicles.
VCA Certification Portal
Type-approval guidance and documentation.
Records are subject to review and correction. Source links, dates and verification notes should be read with the technical information. Our Editorial and Sourcing Policy explains our standards and review process.
Found an error or missing source? Report a problem with this page. Include the field or statement concerned and a supporting source if available. You can also email corrections@enginecode.uk.
Copyright and permissions
Images and other material may be protected by copyright. Attribution does not by itself grant permission to reuse material. If you believe material on this site infringes your rights, contact copyrights@enginecode.uk with the page URL and details of your claim. We will review the material and take appropriate action.
Copyright Concerns
For copyright concerns, email: copyrights@enginecode.uk
Our Privacy Policy explains how Engine Finders UK Ltd uses information from visits, vehicle lookups, enquiries and messages. Our Cookie Policy explains cookies and similar technologies and how to change your choices.
For access, correction, or deletion requests, email: gdpr@enginecode.uk
Trademark Notice
All trademarks, logos, and engine codes are the property of their respective owners. Use on this site is strictly for reference and identification.
Ownership and commercial services
EngineCode.uk is owned and operated by Engine Finders UK Ltd. Alongside our reference content, we offer an optional replacement-engine enquiry service through Engine Finders and may identify relevant services provided by businesses connected with us. These commercial connections are disclosed. Using an enquiry service is not required to read our reference content.
Engine Finders UK Ltd operates this website. Our optional enquiry service has a commercial purpose. Our Ownership and Commercial Disclosure explains the relationship between the reference website and that service. Participating suppliers pay a fee or subscription to participate on the network and receive quote requests.
Use this record as a starting point for identification. Specifications and vehicle applications may contain errors or omissions. Confirm the exact engine variant and compatibility using vehicle-specific documentation and a qualified supplier or technician.
All external links open in new tabs. Please verify current availability of resources.