Exhaust gas analysis

EXHAUST GAS ANALYSIS

Table summarizing pollutant emission tolerance values

Checking concentration of CO and HC at the exhaust

The exhaust concentration of carbon monoxide (CO) and unburnt hydrocarbons (HC) is measured by inserting a suitably calibrated tester sensor 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 value is outside of the recommended limit, whilst that measured previously upstream of the catalyzer was correct, 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 with the one recommended, as the system is the self-adjusting type 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.

IGNITION ADVANCE CHECK

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