Exhaust gas analysis

EXHAUST GAS ANALYSIS

Table summarizing pollutant emission tolerance figures

Checking exhaust concentration of CO and HC

The concentration of carbon monoxide (CO) and unburnt hydrocarbons (HC) at the exhaust is measured by inserting a suitably calibrated tester at least 30 cm into the end of the exhaust pipe.

1. Check that the idle CO and HC concentrations correspond to the recommended figures (see table).
2. If the HC figures are outside of the recommended limits, whilst those measured previously, upstream of the catalyzer were okay, then the engine parameters are correct and the cause of the problem should therefore be sought in the decreased efficiency of the catalyzer.

CHECKING ENGINE IDLE SPEED

If the engine idle speed does not correspond to the recommended figure and the system is the self-adjusting type, then no adjustments can be carried out: it is therefore necessary to check that the accelerator linkage is correctly adjusted and the cause of the problem should be sought by carrying out a complete fault diagnosis using the diagnostic equipment.

CHECKING IGNITION ADVANCE

The diagnostic equipment must be used to check the ignition advance angles at different speeds.