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Eleven experienced commercial automotive technicians were recruited and trained to repair IM240 emission failures using a specially developed 30 hour course. The training course emphasized the use of an oscilloscope and a flow chart and wave form strategy to repair vehicles. Each technicians' performance was evaluated based on the repair of three or four in-use Arizona IM240 failures. Pre-training and post-training written tests were also administered. Results from this limited study were encouraging. After the technician training, HC and CO emission levels were reduced by 69% and NOx by 58%. More importantly, most of the technicians learned some new and useful diagnostic and equipment skills which they can immediately apply to their businesses. They also became more motivated to tackle the challenge of repairing vehicles to low transient emissions, and aware of the existence and use of new sophisticated diagnostic tools such as oscilloscopes.

Two new, low cost methods used to identify inefficient or damaged catalytic converters were evaluated on in-use vehicles. The first technique was a non-intrusive propane injection catalyst test procedure developed by General Motors as part of their overall diagnostic strategy. The second technique utilized an Olympus fiber-optic borescope to visually assess the condition of catalytic converter substrates. Results from the two new techniques were compared against those from standard modal catalyst testing and IM240 tailpipe emission testing. The test results from seventy vehicles show the propane injection test to be generally effective at discriminating between converters with high and low conversion efficiencies. The fiber-optic borescope was less successful in identification of inefficient catalysts. This is because some catalyst failures are not readily identifiable while others have identifiable problems, but continue to perform at reasonable efficiencies.

A Remote Sensing Device (RSD) was used to measure on-road emissions of carbon monoxide (CO), hydrocarbons (HC, propane equivalent), and carbon dioxide (CO2) from vehicles as they entered and exited a centralized Arizona Inspection and Maintenance (I/M) lane conducting a steady-state dynamometer test. Approximately 16,000 RSD measurements were collected and matched with I/M records from 9,000 vehicles. The RSD demonstrated approximately a 90 percent success rate in recording emissions and license plates. When moderate RSD pass/fail standards were applied to the data, approximately 41 percent of the 1981 and later I/M failures were identified based on a single RSD measurement. When the minimum reading from two RSD tests was used, only 20 percent of the I/M failures were identified. However, virtually all of the vehicles that failed two RSD tests were I/M failures.

Twenty in-use vehicles that had failed the I/M test in the State of Michigan were inspected for engine mechanical condition as well as the state of the emission control system. Mass emission tests were conducted before and after repairs to the emission control system. The internal engine condition (i.e., high or low levels of cylinder leakage, or compression difference) showed little effect on the ability of the repaired vehicles to achieve moderate mass emission levels. Nine of the twenty vehicles were recruited after three years, and with the exception of tampering, the original emission control system repairs proved to be durable.

There has been considerable interest in applying remote measuring methods to sample in-use vehicle emissions, and to characterize fleet emission behavior. A Remote Sensing Device (RSD) was used to measure on-road carbon monoxide (CO) emissions from approximately 350 in-use vehicles that had undergone transient mass emission testing at a centralized I/M lane. On-road hydrocarbon (HC) emissions were also measured by the RSD on about 50 of these vehicles. Analysis of the data indicates that the RSD identified a comparable number of the high CO emitters as the two speed I/M test only when an RSD cutpoint much more stringent than current practice was used. Both RSD and I/M had significant errors of omission in identifying High CO Emitters based on the mass emission test. The test data were also used to study the ability of the RSD to characterize fleet CO emissions.

In the 1990's there will be a different mix of vehicle technologies than existed in the late 1970's when inspection/Maintenance (I/M) programs were first mandated. These changes include the widespread use of “closed-loop” computer control of engine parameters and fuel injection. Several studies by EPA are examined to determine the effect of these changes on existing I/M programs and to investigate new methods of vehicle inspection. The report discusses the effectiveness of a standard idle emission test versus other inspection methods, the role of proper preconditioning, self-diagnostic trouble code checks as a method to identify high emitting vehicles, uncertainties in predicting tampering and misfueling rates for the future, problems with decentralized programs, and the effectiveness of I/M repairs in reducing vehicle emissions as measured on the Federal Test Procedure.