Diagnosis Using an Exhaust Gas Analyzer

Use of a four or five gas exhaust analyzer can be helpful in troubleshooting both emissions and driveability concerns. Presently, shop grade analyzers are capable of measuring from as few as two exhaust gasses, HC and co, to as many as five. The five gasses measured by the latest technology exhaust analyzers are: HC, CO, CO2, O2 and NOx. Remember, HC, CO, CO2, and NOx are measured in Enhanced I/M programs.

All five of these gasses, especially O2 and CO2, are excellent troubleshooting tools. Use of an exhaust gas analyzer will allow you to narrow down the potential cause of driveability and emissions concerns, focus your troubleshooting tests in the area(s) most likely to be causing the concern, and save diagnostic time. In addition to helping you focus your troubleshooting, an exhaust gas analyzer also gives you the ability to measure the effectiveness of repairs by comparing before and after exhaust readings.

In troubleshooting, always remember the combustion chemistry equation: Fuel (hydrogen, carbon, sulfur) + Air (nitrogen, oxygen) = Carbon dioxide + water vapor + oxygen + carbon monoxide + hydrocarbon + oxides of nitrogen + sulfur oxides

In any diagnosis of emission or driveability related concern, ask yourself the following questions:

• What are the "baseline" exhaust readings? At idle, 2500 rpm, acceleration, deceleration, light load cruise, etc.

• Which sub-system(s) or component(s) could cause the combination of exhaust gas readings measured?

Do It Yourself Car Diagnosis

Do It Yourself Car Diagnosis

Don't pay hundreds of dollars to find out what is wrong with your car. This book is dedicated to helping the do it yourself home and independent technician understand and use OBD-II technology to diagnose and repair their own vehicles.

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