ASE L1 engine performance Exam Study Questions and Answers

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FIRST PUBLISH OCTOBER 2024




ASE L1 engine performance Exam Study
Questions and Answers

Air fuel ratio (Very rich) 10.1 at all speeds




———- Idle Off idle Cruise


HC 250ppm 275ppm 300ppm


CO 3%. 3%. 3%


CO2 7 to 9 all down


O2 .2% all down




What can the possible cause be ?




A. Leaking injector


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, ©GRACEAMELIA 2024/2025 ACADEMIC YEAR. ALL RIGHTS RESERVED

FIRST PUBLISH OCTOBER 2024




B. High Map sensor voltage (low pressure reading) (vacuum leak)


C. Stuck open thermostat


D. All the above - Ans:✔✔-D


Air fuel ratio (Rich) 10.1 to 12.1 at low speed




————Idle —-Off idle —-Cruise


HC —-150ppm —150ppm ——-100ppm


CO ——-1.5%. ———1.5%. ———-1.5%


CO2— 7 to 9% —7 to 9% ——11 to 13%


O2 —- .5% ——-.5% ———- 1.0




High Map sensor (vacuum leak)


Leak injectors


Engine oil diluted with gasoline




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FIRST PUBLISH OCTOBER 2024




Excessive crankcase blowby


Stuck open thermostat


And....


What else can cause this condition?


A. Low fuel pressure


B. Bad camshaft


C. High fuel pressure


D. All the above - Ans:✔✔-C


Air fuel ratio very lean above 16.1 at all speeds




————Idle —-Off idle —-Cruise


HC —-200ppm —205ppm ——-250ppm


CO ——-.5%. ———.5%. ———-1.0%


CO2— 7 to 9% —7 to 9% ——7 to 9%




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FIRST PUBLISH OCTOBER 2024




O2 —- 4-5% ——-4-5% ———- 4-5%




Intermittent ignition problems (misfire)


Restricted fuel injector


Low fuel pressure


Vacuum leak


Improper timing


And..


What else could cause this concern?




A. Stuck open thermostat


B. Stuck close thermostat


C. Both b and d


D. Low cylinder compression - Ans:✔✔-C
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