The Fiat 138 A4.000 – Petrol is a 1,585 cc inline-four naturally aspirated engine produced between 1980 and 1984. It features a single overhead camshaft (SOHC), 8-valve configuration, and twin-choke carburettor fuel delivery, producing 59 kW (80 PS) at 5,600 rpm. Designed as a durable, serviceable powerplant for Fiat’s mid-size family sedans, it utilises a cast-iron block with an aluminium cylinder head and chain-driven camshaft for longevity.
Fitted to the Fiat 138 and 138 Super models, the A4.000 engine was engineered for balanced performance and ease of maintenance in urban and rural environments. It was paired with a 4-speed manual transmission and featured electronic ignition and a dual exhaust system on higher trims. Emissions compliance was achieved through exhaust gas recirculation (EGR) and thermal reactor technology, allowing adherence to EU Directive 70/220/EEC (Phase II) in key European markets.
One documented service concern involves valve guide wear observed in high-mileage units, particularly under sustained high-load operation or inadequate oil maintenance. This issue was addressed in Fiat Technical Bulletin TB-ME-027 (1981), which recommended revised valve stem seal specifications and specified use of upgraded nitrile-based seals to reduce oil consumption and improve idle stability.
Production years 1980–1982 comply with EU Directive 70/220/EEC (Phase II); 1983–1984 models may meet national Italian emissions standards depending on market (VCA UK Type Approval #VCA/EMS/5682).
The Fiat 138 A4.000 – Petrol is a 1,585 cc inline-four naturally aspirated engine developed for mid-size sedans (1980–1984). It combines SOHC valvetrain architecture with twin-choke carburettor fuel delivery to deliver predictable performance and mechanical simplicity. Designed to meet evolving EU emissions standards, it balances durability with everyday drivability.
| Parameter | Value | Source |
|---|---|---|
| Displacement | 1,585 cc | |
| Fuel type | Petrol | |
| Configuration | Inline-4, SOHC, 8-valve | |
| Aspiration | Naturally aspirated | |
| Bore × stroke | 78.0 mm × 82.0 mm | |
| Power output | 59 kW (80 PS) @ 5,600 rpm | |
| Torque | 122 Nm @ 3,200 rpm | |
| Fuel system | Weber 32/36 DGV twin-choke carburettor | |
| Emissions standard | EU Directive 70/220/EEC (Phase II) | |
| Compression ratio | 9.0:1 | |
| Cooling system | Water-cooled | |
| Turbocharger | Not applicable | |
| Timing system | Chain-driven camshaft | |
| Oil type | SAE 10W-40 (API SF) | |
| Dry weight | 140 kg |
The SOHC carburetted design offers predictable throttle response but requires periodic adjustment of the twin-choke carburettor to maintain drivability. SAE 10W-40 API SF oil is essential for camshaft and valve train protection under sustained load. Regular valve clearance checks (every 20,000 km) prevent noise and performance loss. The valve guides are prone to wear in high-mileage units; post-1981 models benefit from upgraded nitrile seals per TB-ME-027. Thermal reactor and EGR systems must remain intact for compliance in regulated markets. Coolant system maintenance—including thermostat and radiator inspection—is critical to prevent overheating and head distortion.
Oil Specs: Requires SAE 10W-40 API SF specification (Fiat TB-ME-027). Zinc content critical for flat-tappet cam protection.
Emissions: EU Directive 70/220/EEC Phase II applies to 1980–1982 models (VCA Type Approval #VCA/EMS/5682). 1983–1984 units meet national Italian standards.
Power Ratings: Measured under UN ECE Regulation 85. Output varies slightly with carburettor calibration and altitude (Fiat TIS M138-ENG-01).
Fiat Technical Information System (TIS): Docs M138-ENG-01, M138-FUEL-01, TB-ME-027
VCA Type Approval Database (VCA/EMS/5682)
UN ECE Regulation 85: Measurement of Power of Engine Types
The Fiat 138 A4.000 – Petrol was used across Fiat's 138 series platform with longitudinal mounting and utilised in both standard and uprated configurations. This engine received application-specific adaptations—performance cam profiles in the Super variant and emissions control hardware in export markets—and from 1981 incorporated upgraded valve stem seals and revised EGR calibration, creating service differentiation. All adaptations are documented in OEM technical bulletins.
Locate the engine number stamped horizontally on the right-side engine block near the transmission bellhousing (Fiat TIS M138-ID-01). The fifth character of the VIN indicates engine type ('A' for A4.000 series). Pre-1981 models have chrome valve covers with Weber carburettor; post-1981 units use black valve covers with updated gasket. Critical differentiation from 2.0L variants: A4.000 has 78 mm bore (measurable via spark plug hole) and uses a smaller intake manifold. Service parts require model-year verification—valve stem seals before 05/1981 are incompatible with later units due to material upgrade (Fiat TB-ME-027).
The A4.000's primary reliability risk is valve guide wear on pre-1981 units, with elevated incidence in high-mileage or poorly maintained examples. Internal Fiat service reports from 1982 indicated a notable number of early engines required valve service before 90,000 km, while VCA historic vehicle inspection data shows carburettor and ignition faults dominate emissions test failures. Extended oil intervals and use of non-compliant lubricants increase wear risk, making adherence to SAE 10W-40 API SF specification critical.
Analysis derived from Fiat technical bulletins (1980-1985) and UK VCA historic vehicle inspection data (1980-2023). Repair procedures should follow manufacturer guidelines.
Find answers to most commonly asked questions about FIAT 138-A4-000.
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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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