Contents: Verification conditions ⇓ Examination ⇓
The purpose of this test is to confirm that the CO/CH content in engine exhaust gases complies with the legal requirements for the toxicity of exhaust gases from vehicle engines.
Verification conditions
The engine is warmed up to normal operating temperature.
An air filter is installed in the engine intake system.
All hoses and pipes of the intake system are connected to the corresponding fittings.
All auxiliary equipment (air conditioner, consumers of electrical energy) turned off.
All vacuum lines (hoses and pipelines) connected to the corresponding fittings.
All electrical connectors of the fuel injection system are connected.
The initial ignition timing angle must be adjusted correctly.
The automatic transmission control lever is in neutral position.
The additional tachometer for measuring the engine crankshaft speed and the device for measuring the concentration of CO/CH in the exhaust gases must be calibrated in accordance with the instructions in the operating instructions for these devices.
Examination
Start the engine.
Increase the engine speed to 2500 min⁻¹ and let the engine run at this speed for about three minutes.
Leave the engine idling.
Insert the probe of the device for measuring the concentration of CO/CH in exhaust gases into the exhaust pipe to a depth of at least 40 cm.
Immediately check the readings of the device for measuring the concentration of CO/CH in the exhaust gases with the engine idling and/or at a crankshaft speed of 2500 min⁻¹.
Note: When measuring the CO/CH concentration in the exhaust gases at elevated engine speed, the engine speed value must comply with the legislation requirements of the country where the vehicle is operated and may differ from the value given in the test procedure description (2500 min⁻¹).
[Content based on information from: MAZBOOK.RU]
If the concentration of CO/CH in the engine exhaust gases does not comply with the legal requirements for exhaust gas toxicity, it is necessary to find out the reason for this discrepancy and eliminate it. The procedure for finding the cause of the increased CO/CH content in the exhaust gases is given below.
With normal CO content in the exhaust gases and increased CH content (uneven engine operation at idle may also be observed) please do the following checks (checks must be performed in the order in which they are listed):
- check the engine ignition system (correct setting of the ignition timing angle, condition of the spark plugs: functionality, size of the gap between the electrodes);
- check the clearances in the valve drive mechanism;
- check for leaks (in closed state) through the intake and exhaust valves;
- check the condition of the engine cylinder-piston group.
With reduced CO content in the exhaust gases and increased CH content (uneven engine operation at idle and instability of instrument readings when measuring CH may also be observed) please do the following checks (checks must be performed in the order in which they are listed):
- check for air leaks in the intake system - in the engine crankcase ventilation system, in the intake manifold connections, in the receiver connections, in the throttle valve unit connections, through the idle speed control valve;
- check for air leaks through leaks in the brake booster hose connections;
- check the fuel injection system for proper operation (misfiring may occur when the engine is running on a lean fuel-air mixture) (with a working ignition system), which leads to an increase in the concentration of unburned hydrocarbons (CH) in the exhaust gases.
With increased CO content in the exhaust gases and increased CH content (you may also notice uneven engine idling and black smoke from the exhaust pipe) please do the following checks (checks must be performed in the order in which they are listed):
- check the condition of the engine air filter;
- check the idle speed control valve for proper operation;
- check the serviceability of the fuel injection system components: fuel pressure regulator, coolant temperature sensor, fuel injection system electronic control unit, fuel injectors, throttle position sensor, air flow sensor.