Final answer:
Spark plug fouling is not caused by a plugged air filter in an engine, while other issues like hard starting, loss of power, and high compression can be impacted by a blocked air filter.
Explanation:
Spark plug fouling is not typically caused by a plugged air filter in an engine. The other issues mentioned, such as hard starting, loss of power, and high compression, can occur due to a blocked air filter affecting air intake.
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