API 4637 : 1995

ANALYSIS OF CAUSES OF FAILURE IN HIGH EMITTING CARS

American Petroleum Institute

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Executive summary
1 Introduction
    Organization of the report
2 Analysis of diagnostic data
    Database description
    Cooperative test program (CTP) data
    EPA Indiana data
    EPA Arizona data
    CARB fuel-injected (CARBFI) vehicle study
    CARB I/M pilot project data
    Summary statistics
    Database reformatting
    Emission reductions from repair
    Methodology to estimate the effects of individual
    component repair
    Results of the regression analysis
    Excess emissions versus nature of defect
    Prevalence of emission control system defects in
    the fleet
    Hammond and Phoenix component failure rates
    CARB I/M pilot project component failure rates
    Overall impact of specific defects on fleet-average
    emissions
    PCV system defects
3 Review of CARB'S OBDII analysis
    Data description and summary statistics
    Component failure rates
    Effect of component repair
    Methodology
    Average emission reductions from individual repairs
    Fleet-average emission reductions
4 Review of EPA and CARB recall data
    References
Appendix A
Regression results for analysis of FTP reductions from
repairs

Abstract

Describes an investigation to evaluate the primary causes of high exhaust emissions from light-duty vehicles on the road. It is an analysis of emissions data from tests previously conducted by the U.S. EPA, the California Air Resources Board, and one joint EPA-industry program. The analysis involves a comparison of emissions test data collected both before and after the performance of repairs on 1981 and newer cars and trucks. Emission control defects, their prevalence and overall contribution to fleet emissions are described.