Engine Mitsubishi 4A31

The Mitsubishi 4A31 1.1-liter gasoline engine was produced in Japan from 1995 to 2001 and was installed on local kei cars, including the rather popular Pajero Junior. In addition to the injection version of the unit, there was a modification with direct fuel injection.

The 4A3 family also includes engines: 4A30.

The engine was installed on:

  • Mitsubishi Pajero Junior (H57) in 1995 – 1998;
  • Mitsubishi Pistachio H44 in 1999 – 2000;
  • Mitsubishi Toppo BJ Wide H43A in 1999 – 2001;
  • Mitsubishi Town Box Wide U65 in 1999 – 2001.

Specifications

Production years 1995-2001
Displacement, cc 1094
Fuel system distributed injection (4A31 ECI)
direct injection (4A31 GDI)
Power output, hp 78 (4A31 ECI)
74 (4A31 GDI)
Torque output, Nm 103 (4A31 ECI)
100 (4A31 GDI)
Cylinder block cast iron R4
Block head aluminum 16v
Cylinder bore, mm 66
Piston stroke, mm 80
Compression ratio 9.5 (4A31 ECI)
11.0 (4A31 GDI)
Features SOHC (4A31 ECI)
DOHC (4A31 GDI)
Hydraulic lifters no
Timing drive belt
Phase regulator no
Turbocharging no
Recommended engine oil 5W-30
Engine oil capacity, liter 3.5
Fuel type 92 (4A31 ECI)
95 (4A31 GDI)
Euro standards EURO 2/3 (4A31 ECI)
EURO 4 (4A31 GDI)
Fuel consumption, L/100 km (for Mitsubishi Pajero Junior 1997)
— city
— highway
— combined
9.0
5.5
6.9
Engine lifespan, km ~220 000
Weight, kg 105

Disadvantages of the Mitsubishi 4A31 engine

  • The aluminum head is afraid of overheating and cracks easily if the bolts are overtightened;
  • The engine mounts wear out pretty quickly and the unit starts to vibrate;
  • The timing belt is designed for 90,000 km, and when it breaks, the valves always bend here;
  • Approximately every 50 thousand km it is necessary to adjust the thermal clearances of the valves;
  • By 90,000 km, the rings or caps usually wear out and the oil burn begins.

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