The customer complains of a loss of power at highway speeds and a rough running engine at all speeds. A five-gas analyzer reveals these measurements at 2,500 rpm: HC = 700 ppm, CO = 0.2%, CO₂ = 9.2%, O₂ = 6.2%, and NO _X = 330 ppm. What is the most likely cause?

Question

Quizplus · Accepted Answer

The high HC (hydrocarbons) level indicates unburned fuel, which, along with the normal CO (carbon monoxide) level, suggests incomplete combustion rather than a rich or lean mixture. This scenario is indicative of a lean misfire, where the engine misfires due to a lean fuel mixture, leading to rough running and loss of power.

The Customer Complains of a Loss of Power at Highway