Introduction to the TU3F2K Engine

The Citroen TU3F2K is a 1.4 liter inline-4 gasoline engine that was produced from 1996 to 2005. It was used in several Citroen and Peugeot models, including the Saxo, 106, and 206. The engine features multi-point fuel injection, an overhead camshaft, and 4 valves per cylinder. It produces 75 hp (56 kW) at 5500 rpm and 89 lb⋅ft (121 N⋅m) of torque at 3400 rpm.

TU3F2K Engine Specifications

Specification	Value
Engine Type	Inline-4, SOHC
Displacement	1.4 L (1360 cc)
Bore	75 mm (2.95 in)
Stroke	77 mm (3.03 in)
Compression Ratio	10.2:1
Power	75 PS (55 kW; 74 hp) at 5500 rpm
Torque	121 N⋅m (89 lb⋅ft) at 3400 rpm
Fuel System	Multi-point fuel injection
Engine Management	Magneti Marelli 1AP
Valvetrain	SOHC, 4 valves per cylinder

TU3F2K Engine Components and Schematics

Cylinder Block

The TU3F2K engine uses a cast iron cylinder block with five main bearings. The block is an open-deck design for improved cooling. The cylinder bores are 75 mm in diameter.

Cylinder Head

The cylinder head is made of aluminum alloy and features a single overhead camshaft (SOHC) with roller rocker arms. There are four valves per cylinder (two intake, two exhaust) actuated by the camshaft.

Camshaft

The camshaft is driven by a timing belt and features an intake valve duration of 226 degrees and exhaust duration of 226 degrees. Valve lift is 7.3 mm on the intake side and 6.8 mm on the exhaust side.

Pistons

The pistons are made of aluminum alloy. Each piston has two compression rings and one oil control ring.

Connecting Rods

The connecting rods are forged steel. The big end bore diameter is 45 mm and the small end bore diameter is 18 mm.

Crankshaft

The crankshaft is forged steel with five main bearing journals and four rod bearing journals. Main journal diameter is 47.8 mm and rod journal diameter is 39.8 mm. Total crankshaft length is 379.4 mm.

Engine Lubrication System

The TU3F2K engine uses a pressure lubrication system with an oil pump driven by the crankshaft. The oil pump is located in the oil pan and has a capacity of 17.6 cc/rev. Oil pressure at idle is 0.8 bar (11.8 psi).

Cooling System

The cooling system consists of a water pump, radiator, thermostat, and hoses. The water pump is driven by the timing belt. Coolant capacity is 4.3 liters.

Fuel System

The TU3F2K engine uses a returnless multi-point fuel injection system with an electric fuel pump mounted in the fuel tank. Fuel pressure is regulated to 3 bar by the fuel pressure regulator. The fuel injectors are side-feed design with 4 holes.

Intake and Exhaust

The intake manifold is plastic and features a resonance chamber for improved low-RPM torque. The throttle body has a diameter of 45 mm. On the exhaust side, the manifold is made of cast iron and converges into a single pipe before entering the catalytic converter.

Engine Management System

The TU3F2K’s engine management system is a Magneti Marelli 1AP ECU. It controls fuel injection, ignition timing, and idle speed. The ECU receives input from various sensors including:

• Crankshaft position sensor
• Camshaft position sensor
• Coolant temperature sensor
• Intake air temperature sensor
• Throttle position sensor
• Oxygen sensors

Based on these inputs, the ECU optimizes engine performance, efficiency, and emissions.

TU3F2K Engine Performance

Power and Torque Curves

The TU3F2K engine produces a maximum of 75 PS (55 kW; 74 hp) at 5500 rpm and 121 N⋅m (89 lb⋅ft) of torque at 3400 rpm. Here is the full power and torque curve:

RPM	Power (PS)	Torque (N⋅m)
1000	15	71
2000	37	104
3000	58	119
4000	71	119
5000	75	109
6000	71	91

Fuel Economy

The TU3F2K engine offers good fuel efficiency for its era and displacement. In the Citroen Saxo 1.4i, it achieves the following rated fuel economy:

• Urban: 7.6 L/100 km (31 mpg US / 37 mpg UK)
• Extra Urban: 4.9 L/100km (48 mpg US / 58 mpg UK)
• Combined: 5.9 L/100 km (40 mpg US / 48 mpg UK)

Emissions

With its multi-point fuel injection and catalytic converter, the TU3F2K engine meets Euro 3 emission standards. CO emissions are rated at 0.46 g/km, HC at 0.04 g/km, and NOx at 0.02 g/km.

Maintenance and Repair

Regular Maintenance

To keep a TU3F2K engine running properly, regular maintenance should be performed at the following intervals:

Item	Interval
Engine Oil and Filter	10,000 km or 12 months
Air Filter	30,000 km
Fuel Filter	30,000 km
Spark Plugs	30,000 km
Timing Belt	90,000 km or 5 years
Coolant	60,000 km or 4 years

Common Issues and Repairs

Some common issues with the TU3F2K engine include:

• Timing belt failure: If the timing belt breaks, it can cause major engine damage. Replacing it every 90,000 km or 5 years is key.

• Oil leaks: Leaks from the timing cover gasket, cylinder head gasket, and crankshaft seals are not uncommon.

• Thermostat failure: A stuck-open thermostat can cause poor engine warm-up and heater performance.

• Idle control valve: The idle control valve can become clogged, causing rough idle and stalling.

• Oxygen sensors: Failed O2 sensors can cause poor fuel economy and higher emissions.

Many of these issues can be prevented with regular maintenance. When problems do occur, early diagnosis and repair is important to prevent further damage.

Conclusion

The Citroen TU3F2K is a reliable and efficient engine that powered many popular French compact cars in the late 1990s and early 2000s. With its multi-point fuel injection, SOHC 4-valve design, and low-friction internals, it offered a good balance of performance and economy for its time.

While not the most powerful or advanced engine by modern standards, the TU3F2K remains a solid choice for those seeking an affordable and dependable powerplant. With proper maintenance and care, it can provide many years of trouble-free service.

Frequently Asked Questions

1. What type of oil should I use in a TU3F2K engine?

The recommended oil for the TU3F2K engine is 5W-40 synthetic oil meeting API SJ or higher standards. Capacity is 3.25 liters with filter.

2. What is the firing order of the TU3F2K engine?

The firing order is 1-3-4-2. Cylinder #1 is at the timing belt end of the engine.

3. Can I improve the performance of my TU3F2K engine?

Some popular modifications for the TU3F2K include cold air intakes, cat-back exhausts, and ECU tuning. These can provide modest gains in power and torque. More significant upgrades like camshafts, porting, and forced induction are possible but may not be cost-effective.

4. How do I set the timing on a TU3F2K engine?

Correct timing belt installation is critical. The cam and crank sprockets have timing marks that must be aligned properly. Special tools are required to lock the cam and crank in position. It’s best to refer to a service manual or leave this job to a professional.

5. What are the symptoms of a failing TU3F2K timing belt?

Symptoms of a failing timing belt include rough running, loss of power, and a rattling noise from the front of the engine. If the belt breaks while driving, the engine will stop suddenly and will not restart. If this happens, significant valve and piston damage can occur.