Auto emissions testing: Designed for failure

Published April 1, 2000

The U.S. Environmental Protection Agency’s IM-240 auto emissions test, used in a few states but rejected by others for its tendency to cause serious vehicle damage, is also likely to show false test failures, particularly in cool weather, according to automotive experts.

The IM-240 dynamometer or “treadmill” test takes longer to run than did the familiar “idle” emissions test. Compounding the delay is the fact that emissions testing centers generally employ relatively unskilled technicians, according to Robert Brooks, correspondent for the automotive trade publication Ward’s Engine and Vehicle Technology Update.

As a result of the delays, Brooks points out in a recent issue of the publication, a vehicle’s catalytic converter–a key component of its emissions control system–can cool down to the point where it no longer functions.

Edwin Martin, an automotive consultant to the Texas State Inspection Association and other industry groups, confirmed Brooks’ conclusions for Environment & Climate News. Martin noted that catalytic converters must be heated by engine exhaust to at least 500-600 degrees Fahrenheit to function effectively. He said that idling at low temperatures for as little as 10 minutes in a cool climate could drop converter temperatures below their minimum operating temperatures.

Brooks pointed out that motorists often wait longer that 10 minutes in Chicago’s frigid winter weather. He said test station attendants often have motorists turn their engines off while waiting, further exacerbating the problem.

New Jersey, which also uses the EPA-preferred IM-240 test, experienced waiting times so long that the state’s governor, Christine Todd Whitman, sought relief from EPA. In a just-reached agreement, EPA permitted the state to revert to the older, quicker idle test, but only for cars that had been waiting in line at least 45 minutes.

In addition to the effect of delays on catalytic converters, Ward’s Brooks also cited other reasons why non-polluting cars nevertheless fail the test, including incorrect dynamometer settings and improper or even abusive testing by technicians.

Automotive industry experts say the only reason vehicles pass the misused test at all is the advances in engine design that have occurred in the last decade, notably advanced fuel injection, oxygen sensing and regulating systems, and close-tolerance machining.

The IM-240 test has been the subject of controversy since its inception. Automotive experts contend it is no more effective than the older, far less costly idle test it replaced at detecting “gross-polluting vehicles”–the source of the vast majority of automotive pollution emissions.

And unlike the idle test, the IM-240 has been shown to result in serious damage to tested vehicles. Since the IM-240’s launch in February 1999, there have been numerous complaints of vehicle damage, ranging from tire destruction to brake, engine, and transmission failures, according to reports received by Environment & Climate News. In Illinois, the state EPA has declined to provide specific information on vehicle damage claims, but a lawsuit filed in Chicago may make those records public. Ohio discontinued the test in favor of a simpler version, and the IM-240 is also being challenged in Arizona and California.