Possible malfunctions of the engine management system, their causes and methods of elimination (Focus 2)

Cause of malfunction	Method of elimination
The starter rotates the crankshaft at normal speed, but the engine does not start for a long time. After starting, the engine immediately stops
The ignition system is faulty	Check the voltage in the secondary circuit; condition of spark plugs (carbon deposits, electrode moisture, cracks or chips in the insulator, condition of the electrodes and gap); ignition coils, high-tension wires and protective caps; reliability of electrical contact in ignition coil connectors; reliability of contacts between the EEU and the "ground"
The fuel injection system is faulty	See "Engine Fuel System", p. 113
The engine does not develop its rated power. The car accelerates sluggishly when the accelerator pedal is pressed partially
The ignition system is faulty	Check the voltage in the secondary circuit with a special tester. Check the operation of the ignition timing system with a stroboscope
There is no reliable contact between the ECU and the ground	Check the condition, cleanliness and tightness of the connections of the terminals of the ECU ground wires
Low voltage in the on-board network - the generator is faulty	Check the voltage at the "B+" terminal of the generator, which should be at least 13 V
Detonation knocks in the engine when accelerating the car
Incorrect heat range of spark plugs installed on the engine	Replace spark plugs with those recommended for this engine model
Damage to high voltage wires	Check the resistance of the high-voltage wires with an ohmmeter. It should not exceed 30 kOhm. The ohmmeter is connected to the tips of the wire being tested
Malfunction of the coolant temperature sensor or its electrical circuit	Check and replace the sensor if necessary. Check the contact connections in the sensor circuit wiring
Lack of quick engine response to changes in throttle position, especially when starting the car from a standstill and at the beginning of acceleration
Throttle position sensor is faulty	Replace the sensor
Low voltage in the on-board network - the generator is faulty	Check the voltage at the "B+" terminal of the generator with a voltmeter when the engine is running; it should be more than 13 V
The mass air flow sensor is faulty	Replace the sensor
High voltage wires are faulty	Check the resistance of the wire with an ohmmeter. Connect it to the tips of the wire being tested. The resistance should be no more than 30 kOhm
The spark plugs are dirty	Sandblast or replace spark plugs
Contamination of ignition devices	Remove moisture and dirt from high tension wires and ignition coil
Unreliable contact of ignition devices with the "ground"	Check the ignition system wire connections to ground. Clean and tighten the wire ends
Engine runs intermittently. Car jerks when engine load increases. Uneven noise when exhausting
Spark plug failure	Start the engine. After setting the idle speed, remove the high-tension wire from one spark plug using pliers with insulated handles. Disconnect the wires from the spark plugs one at a time and for a short time so as not to damage the catalytic converter. If disconnecting the wire from the spark plug does not cause a sharp decrease in engine speed, then the spark plug is faulty and must be replaced
High voltage wires fault	Measure the resistance of the wires between the tips with an ohmmeter, which should be no more than 30 kOhm
Uneven engine idling, accompanied by increased vibration and stalling
Lean air-fuel mixture due to increase in oxygen concentration sensor signal voltage due to deposits on the sensor bulb	If there is a white powdery deposit on the sensor, replace it
Throttle valve stuck open	Fix a sticking throttle valve
Malfunction of the coolant temperature sensor or its electrical circuit	Check and replace the sensor if necessary. Check the contact connections in the sensor circuit wiring

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Article reviewed: Mikhail Dmitriev

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Design features of the engine management system

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Checking the ignition coil
Removing and installing the ignition coil
Removal and installation of the electronic engine control unit
Checking and replacing engine management system sensors

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