AIR FUEL RATIO

5 Gas Analysis

5 Gas Analysis

• Now that you know about each gas individually, we will use the following charts to see how the gases relate to each other.

• Because of the Catalytic Converter these relationships will look a little different on an emissions test, but are a great place to start for determining why a gas or combination of gases is out of range.

• CO2 is an combustion efficiency indicator.• O2 is a lean condition indicator.• CO is a rich mixture indicator.• HC is a misfire indicator.

STOICHIOMETRIC CHART

14.7:110:1 20:1RICH LEAN

5 Gas Analysis• The converter can reduce a lot of NOX, HC & CO but

is has limits.• If the gases are over 4% CO or 400ppm HC the Cat.

not only can’t process the gases it will destroy itself trying.

• So if you diagnosis and replace a failed converter and the gas levels are near these amounts the new converter will quickly burn out. Diagnosis the root cause first!

• The VIR does not tell the whole story, but using 5 gas analysis you can narrow down the possibilities.

• Having a clear idea of what is not wrong saves diagnostic time.

• Repairing one gas may create another gas failure.

Diagnosing by Gas Failure

• As you have seen, analyzing the 5 gas content of the engine exhaust will allow you to isolate the problem quickly, replace the faulty components or make adjustments as required, and get your customer back on the road.

• The most important thing to remember is that the PCM adjusts fuel and ignition timing based on air volume.

• Your 5 gas analyzer is your best attack on driveability complaints on all gasoline vehicles, old or new.

5 Gas Analysis