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1993 Subaru Legacy 4 cyl won't pass smog test

Tiny
2CP-ARCHIVES
  • MEMBER
  • 1993 SUBARU LEGACY
  • 4 CYL
  • 2WD
  • AUTOMATIC
  • 120,000 MILES
My Subaru won't pass smog test. All emission systems have passed but HC 232 at idle 701 rpm and co 2.04 at 701 rpm. The co 1.67 at 2500 rpm. Hc okay. This car runs excellent and has always been maintained and uses no oil but will not pass.
Tuesday, October 19th, 2010 AT 5:04 PM

1 Reply

Tiny
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  • MEMBER
  • 4,540 POSTS
At cruise, the engine is lightly loaded and running at high rpm. Under these conditions, HC and CO should be low if the oxygen sensor and feed back control system are working properly, and the catalytic converter is in good condition. High CO readings during cruise indicate a rich fuel condition. Causes here may include: Defective O2 sensor; Exhaust leaks upstream of the O2 sensor (check manifold gaskets and air plumbing connections. Defective air pump or diverter valve (also loose or damaged air pump plumbing); Defective MAP, MAF or VAF sensor.
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Tuesday, October 19th, 2010 AT 5:06 PM

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