Emissions Testing Vehicle Preconditioning
90buick13Bulletin 91-6E-2
Date Oct. '90
Ref. No. 91-035-6E
Corp. Ref. No. 080101
SUBJECT: VEHICLE PRECONDITIONING PRIOR TO STATE EMISSIONS TESTING
MODELS AFFECTED: ALL MODELS/ALL MODEL YEARS
With increasing concern for air quality, many states and municipalities have instituted vehicle inspection/maintenance (I/M) programs, most of which include tailpipe exhaust emissions testing. Buick desires to do its part both in helping achieve cleaner air and in making sure our customers' vehicles are tested in a satisfactory manner.
Conducting 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 indicates normal 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 converter and exhaust oxygen sensor may not be at their normal operating temperature. This may cause exhaust emissions levels to be artificially high even though the vehicle's emission control systems are functioning properly.
If the vehicle has been turned off or sitting at idle for several minutes, even though the engine coolant temperature gauge indicates normal 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 is running the engine at 2500 rpm for three minutes with the transmission in park or neutral.