Main faults of the engine management system (VW Golf 4)

Before troubleshooting, make sure that the engine is started correctly. When starting a cold or hot engine, do not press the accelerator pedal. After starting a hot engine, you can slightly increase the engine speed by pressing the accelerator pedal.

Also, before troubleshooting, make sure that there is sufficient fuel in the fuel tank, the engine has no mechanical defects, the battery is charged and the starter turns the engine crankshaft at a sufficient speed, the ignition system is in good working order, the fuel system is sealed and free of contamination, the crankcase ventilation hose is clean and the powertrain ground bus is securely connected.

Pre-check the faults recorded in the engine management system memory.

When working on the fuel system, first relieve the pressure in the fuel system.

CAUSE	METHOD OF ELIMINATION
The engine does not start
When the ignition is turned on, the electric fuel pump does not work	Check the electrical circuit supplying voltage to the fuel pump and the reliability of the electrical connectors
The fuse is faulty	Check the integrity and, if necessary, replace the fuel pump or engine control unit fuse
Fuel pump relay is faulty	Check the functionality and, if necessary, replace the fuel pump relay
No voltage supplied to fuel injectors	Check the electrical circuit of the fuel injectors
Difficulty starting a cold engine and engine running intermittently
The temperature sensor is faulty	Check and replace if necessary the coolant temperature and engine air temperature sensors
The engine runs intermittently
Poor contact in electrical connectors of fuel pump power supply circuit	Check the condition, clean and tighten the contacts of the electrical connectors in the fuel pump power supply circuit. Check and, if necessary, clean the contacts of the fuel pump fuse and relay
The amount of fuel supplied to the engine has been reduced	Check the fuel pump performance
Fuel filter contamination	Replace the fuel filter
The fuel pump is faulty	Check the fuel pump for functionality
The fuel injector is faulty	Check and replace fuel injectors if necessary
Unstable engine operation in transient modes
The engine air supply system is leaky	Check and, if necessary, tighten the engine air supply system connections
The coolant temperature sensor or the air temperature sensor entering the engine is faulty	Check and replace if necessary the coolant temperature and engine air temperature sensors
The fuel system is leaking	Visually check the fuel system for leaks. Check the fuel system connections for tightness
Difficulty starting a hot engine
Increased pressure in the fuel system	Check the fuel system pressure and replace the fuel pressure regulator if necessary
The fuel return line between the fuel pressure regulator and the fuel tank is clogged or deformed	Clean or replace the pipeline
Engine acceleration occurs with a delay
Leaky fuel injectors	Check and replace fuel injectors if necessary