ASE Engine Performance A8 Practice Test 2025 – Complete Exam Prep

When evaluating exhaust emissions testing, a scenario where CO2 levels are low and O2 levels are high typically indicates incomplete combustion. This situation suggests that while the engine isn't effectively burning all of the fuel, it is still creating unburned oxygen in the exhaust.

If Technician A asserts that low CO2 and high O2 point to an overly lean mixture, this is plausible since an overly lean air-fuel mixture can prevent sufficient fuel oxidation, resulting in high levels of O2 and low CO2 emissions.

Conversely, if Technician B believes that this combination indicates potential issues such as a functioning exhaust system or problems with combustion efficiency, this too aligns with the provided data. Both interpretations correctly correlate with low CO2 and high O2 emissions, as both conditions can result from various combustion inefficiencies or mixture adjustments.

Ultimately, the correct answer is that both technicians are correct in their assessments regarding the implications of low CO2 and high O2 readings in the context of exhaust emissions testing. This alignment of their conclusions reflects the complexities of engine performance and emissions, illustrating that both can arrive at valid interpretations based on the same data set.