Engine Performance (A8)Question 106 of 120
A vehicle fails an emissions test for high hydrocarbons (HC). This is most commonly associated with:
a.Excessive coolant
b.Low tire pressure
c.Unburned fuel from misfire, ignition, or rich-condition problems
d.A worn wheel bearing
Explanation
High HC indicates unburned fuel escaping into the exhaust, typically from misfires, ignition faults, or an overly rich mixture. Diagnosing the misfire or fuel-control fault reduces HC. A failing catalytic converter can also raise tailpipe HC.
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