CRUISE EMISSIONS
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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Friday, February 1st, 2008 AT 3:58 PM