IM147 Diagnostics

The state of Arizona requires emission testing when initially registering a vehicle in the metropolitan areas surrounding Phoenix and Tucson and for registration renewals. IM147 is the testing protocol used for emission testing of gasoline powered light duty vehicles manufactured between 1981 and 1995. Im147 has replaced the older, less accurate IM240 protocol. For 1996 and newer vehicles, on board diagnostics are used to evaluate engine performance. On board diagnostics accesses engine performance data by connecting directly to the computer built into your car. If you are concerned about passing the Arizona emissions test Hi-Tech Car Care has the equipment and expertise to perform the test no matter the age of your car.

Evaporative Emission Repairs

The evaporative emissions control system is designed to prevent the release of hydrocarbons into the atmosphere and includes various components, depending on the age of the car. The positive crankcase ventilation valve (PCV valve) prevents the release into the atmosphere of gases generated in the engine. The PCV valve redirects these gases into the intake manifold so they can be burned in the engine. The PCV valve should be replaced every 40,000 to 60,000 miles. The Fuel cap on newer vehicles is sealed to prevent the release of gasoline vapors into the atmosphere. The fuel cap seal should be examined periodically to assure that it still functions properly. The charcoal canister is designed to trap fuel vapors and hold them in the canister. the charcoal canister can become clogged and require replacement.

Catalytic Converter

The three main undesirable constituents of automobile exhaust are carbon monoxide, unburned fuel and oxides of nitrogen. A catalytic converter converts these pollutants into carbon dioxide, nitrogen and water. A level of unburned fuel which is too high can cause the catalytic converter to overheat and to melt. A catalytic converter can also be damaged by substances which coat the working surfaces and prevent the exhaust from contacting them. The worst offender in this regard is lead; this is one reason why lead is no longer used as a fuel additive If your catalytic converter is damaged, it must be replaced.

Oxygen Sensors

The oxygen sensor is located in your car’s exhaust stream and measures the concentration of fuel relative to air. This information is sent to your car’s onboard computer which adjusts the incoming fuel/air mixture. Too little air relative to fuel results in unburned fuel and decreased fuel economy. As noted above, too much unburned fuel in the exhaust can damage the catalytic converter. Too much air relative to fuel can cause your engine to run hot and can damage your engine as well as your catalytic converter and oxygen sensor. An oxygen sensor can fail due to buildup of contaminants, such as lead from leaded gasoline, and from normal aging. A failed or failing oxygen sensor must be replaced immediately.