State Emissions Testing Information

90chevy24
GMC NUMBER: 91-6E-15

GROUP: 6E ENGINE EMISSIONS

DATE: SEPTEMBER, 1990

CORPORATE
NUMBER: 080101
SUBJECT: INFORMATION ON STATE EMISSIONS TESTING

MODELS: ALL 1982-91 TRUCKS
With more emphasis being placed on air quality, many states and municipalities have instituted vehicle inspection/ maintenance (I/M) programs, most of which include tailpipe exhaust emissions testing. GMC Truck desires to do its part both in helping achieve cleaner air and in making sure our customers' vehicles are tested in a satisfactory manner. A satisfactory exhaust emissions test includes making sure the vehicle's engine and emission control systems are fully warmed up just prior to conducting the test. An engine coolant temperature gauge that reads operating temperature or a warm radiator hose does not necessarily mean the vehicle is ready to be tested. For example, although the engine coolant temperature gauge may be reading at operating temperature, the catalytic con- verter may not be fully warmed up, which may cause exhaust emissions levels to be artificially high and not representative of whether the vehicle's emission control systems are functioning properly. Therefore, if the vehicle has been turned off or sitting at idle for several minutes, even though the engine coolant temperature gauge indicates the engine is at operating temperature, the vehicle should be driven on the road for a few minutes just prior to starting the official test to ensure that the engine and emission control systems are fully warmed up. An alternative warm up method that can be used and may be more convenient is running the engine at about 2500 rpm for two or three minutes with the transmission in park or neutral.