Gxt Ferret 54 ENGINE DIAGNOSTIC CENTER Manuel d'utilisateur télécharger pdf (Page 84)

High HC combined with High NOx indicates

a lean misfire. Oil being burned will also raise

the temperature and cause NOx formation.

Possible causes are:

• Lean fuel delivery

• EGR system

• Oil burning due to:

Rings

Valves

Guides

High HC combined with High O2 indicates

there is unburned fuel because of a misfire.

Since air is composed of about 21% Oxygen,

each cylinder that misses will add about:

21%

Number of Cylinders in the Engine

For example, one cylinder misfiring in a 6

cylinder engine would add approximately

3.5% oxygen to the exhaust stream (21%

divided by 6 cylinders).

The catalytic converter may mask the HC

portion, but the increase in O2 will still be

observed. It is important that the air injection

system supplying excess O2 to the converter

be disabled during testing so that the O2

reading can be used for diagnosis. Possible

causes are:

• Ignition misfire

• Misfire from mechanical problems

High CO combined with Low O2 indicates

there is a rich mixture. Possible causes are:

• Problems in the air intake system

• PCV problem

• Improperly set mixture

• Malfunction of vapor canister

High HC combined with High CO and High

NOx indicates there is a complete

breakdown in the emission control system.

If the catalytic converter is functioning at all,

it is overwhelmed by emissions at the

exhaust manifold. Possible causes are:

• Catalytic Converter

• ECM

• Sensors

• Wiring

Low CO2 (<10%) generally indicates a bad

air fuel ratio, either rich or lean.

• When combined with High CO (>0.5%)

and High O2 (higher than CO reading),

the catalytic converter is not burning CO

to form O2.

• When combined with High CO (>0.5%)

and Low O2 (lower then CO reading),

the catalytic converter is probably not the

problem. Possible causes are:

Air intake restriction

Fuel delivery problems

7-11

1 2 ... 79 80 81 82 83 84 85 86 87 88 89 ... 101 102

Commentaires sur ces manuels

Pas de commentaire