1993 Buick Skylark C0 % level to high

1993 BUICK SKYLARK
125,211 MILES • 6 CYL • 2WD • AUTOMATIC
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CHEF35
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To car through inspection and it failed because C0 % was at 2.47 when it should be at 1.20. when car is in park or reverse it sounds fine however when in drive it sounds as though there is a hole in the manifold or muffler, I took it in for service and no holes where found. what can cause the CO % to be high, also what could make it sound so loud when in drive only?
Oct 20, 2009 at 11:09 AM
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RASMATAZ
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Too rich of a mixture causing the CO to be high could be caused by the coolant temperature sensor, oxygen sensor, dirty air filter and engine oil contaminated with fuel
Oct 20, 2009 at 11:46 AM