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Project at a Glance

Project Status: complete

Report Published September 1982:

Title: Study of components influencing the deterioration of vehicle emission control

Contractor: Olson Engineering Inc

Contract Number: A0-104-32

Research Program Area: Emissions Monitoring & Control

Topic Areas: Mobile Sources & Fuels


A fleet of eighteen 1979 to 1981 model year vehicles completed an emissions component calibration inspection and test program. The vehicles were selected from those failing one or more emissions standards after completion of a California Air Resources Board (ARB) in-use vehicle surveillance program. The work was performed at the Automotive Research Center of Olson Engineering Inc. (OEI) in Huntington Beach, California.

A baseline CVS-75 emissions test was performed on each vehicle after an initial inspection and repair or adjustment of basic parameters, vacuum hose routing and visible emissions component malfunctions. After the baseline test, inspection of all testable emissions components was completed using new vehicle certification calibration information. Those components not within calibration were replaced. A catalytic converter efficiency test was performed on most catalysts. Additional CVS-75 emissions tests were performed to determine the effectiveness of the repairs.

Of the eighteen vehicles that completed the program, twenty-nine occurrences of emissions levels above standard existed. Upon completion, fourteen occurrences of emissions levels above standard existed and two of those were ten percent or less above standard. Six vehicles passed all three standards after repairs. Five vehicles were still failing one or more standards after all testable components and parameters were found to be within manufacturer specification. The remaining seven vehicles had various identifiable or suspected problems that could not be repaired or confirmed due to expense, unavailable parts or unavailable special test equipment. The fleet reductions in emissions levels were 27%, 45% and 16% for HC, CO and NOx respectively. Fuel economy was unchanged.

It was concluded that bringing all verifiable emissions components within certification specifications does not ensure that the in-use vehicle will be brought into compliance with emissions standards. It was further concluded that the methods and procedures available to a well equipped emissions laboratory facility (and presumably to persons evaluating certification applications) are not sufficient to verify that the broad range of emissions related components are within calibration.


For questions regarding this research project, including available data and progress status, contact: Heather Choi at (916) 322-3893

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