Possible malfunctions of the engine management system, their causes and methods of elimination
| 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, the condition of the spark plugs (carbon deposits, electrode moisture, cracks or chips in the insulator, condition of the electrodes and gap), ignition coils, high-voltage wires and protective caps, reliability of electrical contact in the connectors of ignition coils, reliability of ECU and ignition switch contacts with "mass" |
| The fuel injection system is faulty | Check the fuel pump relay by connecting a test lamp between the "G" terminal of the diagnostic connector and the "ground". The test lamp should light for 2 seconds after the ignition is turned on |
| The engine does not develop its rated power. The car accelerates sluggishly when the accelerator pedal is partially pressed | |
| 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 of the ECU with 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 | Check the freedom of movement of the sensor slider. As the opening angle of the valve increases, the sensor signal voltage should increase proportionally |
| 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, which should be more than 13 V |
| The absolute pressure sensor in the intake manifold is faulty | Check the sensor, wiring connection and sensor vacuum tube installation |
| High voltage wires are faulty | Check the resistance of the wire with an ohmmeter by connecting 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 coils |
| Unreliable contact of ignition devices with the "ground" | Check the ignition system wire connections to ground. Clean and tighten the wire terminals |
| Engine runs intermittently. Car jerks when engine load increases. Uneven noise when exhausting | |
| Spark plug failure | Start the engine. After setting the idle speed, disconnect the idle speed control connector. 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 |
[The text of the article was obtained from the website: chevyman]