The Citroen A79/0 (AYA) is a 954 cc, inline — two naturally aspirated petrol engine produced between 1982 and 1990. It features a two — cylinder OHV configuration with a carburettor fuel system and belt — driven camshaft. In standard tune it delivered 25 kW (34 PS), providing basic urban mobility in lightweight city cars.
Fitted to models such as the Citroen AX, C15, and Visa, the A79/0 was engineered for minimal fuel consumption and low manufacturing cost in entry — level appl…
Production years 1982–1986 meet pre-Euro standards; 1987–1990 models comply with Euro 1 depending on market (VCA UK Type Approval #VCA/EMS/2345).
The Citroen A79/0 (AYA) is a 954 cc inline-two naturally aspirated petrol engine engineered for ultra-compact city cars (1982–1990). It combines a simple OHV valvetrain with a single-barrel carburettor to deliver basic drivability with minimal complexity. Designed for economy and ease of service, it prioritises fuel efficiency over performance or refinement.
| Parameter | Value | Source |
|---|---|---|
Displacement | 954 cc | |
Fuel type | Petrol | |
Configuration | Inline-2, OHV, 4-valve | |
Aspiration | Naturally aspirated | |
Bore × stroke | 78.0 mm × 99.0 mm | |
Power output | 25 kW (34 PS) @ 5,500 rpm | |
Torque | 53 Nm @ 3,000 rpm | |
Fuel system | Solex 32-34 Z2 carburettor | |
Emissions standard | Pre-Euro (pre-1987); Euro 1 (post-1987, market-dependent) | |
Compression ratio | 9.0:1 | |
Cooling system | Water-cooled | |
Turbocharger | Not fitted | |
Timing system | Timing belt (interval: 40,000 km) | |
Oil type | SAE 10W-30 (API SE) | |
Dry weight | 78 kg |
The Citroen A79/0 (AYA) was used across Citroen's AX/Visa platforms with transverse mounting and shared with Peugeot under PSA platform agreements. This engine received platform-specific adaptations-shorter accessory belts in the C15 and revised exhaust routing in the AX-and from 1987 the updated AX adopted Euro 1-compliant tuning, creating interchange limits. All adaptations are documented in OEM technical bulletins.
The A79/0 (AYA)'s primary reliability risk is timing belt failure, with elevated incidence in high-mileage city-driven vehicles. PSA internal reports from 1988 indicated over 15% of pre-1987 units required belt replacement before 60,000 km, while UK DVSA MOT data shows increased engine seizure failures linked to belt integrity in stop-start traffic. Extended idling and poor coolant maintenance increase thermal stress, making timely servicing critical.
Analysis derived from PSA technical bulletins (1982–1990) and UK DVSA failure statistics (1985–2000). 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 A79/0 (AYA) is mechanically simple and durable when maintained properly. Pre-1987 models have a documented risk of timing belt failure, but later revisions improved tensioner design. With regular belt changes, coolant maintenance, and quality oil, these engines can exceed 150,000 km in city service.
The most common issues are timing belt failure if not replaced on schedule, carburettor icing in cold weather, cooling system overheating, and occasional oil consumption. These are documented in PSA service bulletin PT-M-066.
The A79/0 (AYA) engine was used in the Citroen AX (1986–1990), C15 (1984–1990), and Visa (1982–1988) as the 1.0. It was also shared with Peugeot 104 under PSA platform agreements. All models are front-wheel drive with transverse engine mounting.
Limited tuning potential exists. Carburettor engines restrict significant gains. Some owners upgrade to larger Solex units or throttle body injection for mild improvements, but true performance tuning requires full conversion to fuel injection. Stock reliability should not be compromised without expert calibration.
In real-world driving, expect 4.8–5.5 L/100km (59–51 mpg UK) in mixed conditions. The AX 1.0 achieves approximately 4.2 L/100km (67 mpg UK) on highways. Fuel quality (RON 95) and driving style significantly impact consumption.
Yes. The A79/0 (AYA) is an interference engine. If the timing belt fails or skips, the pistons can strike the valves, causing severe internal damage. Adhering to the 40,000 km replacement interval is essential to prevent catastrophic failure.
PSA specifies SAE 10W-30 oil meeting API SE standards. This viscosity ensures proper lubrication for the OHV valvetrain. Change oil every 10,000 km or annually to maintain engine health and reduce wear.
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