What is meant by “improper maintenance” in emissions testing?

Improper maintenance in emissions testing refers to the neglect of regular vehicle maintenance that directly affects the emissions produced by the vehicle. This can encompass a variety of actions, or lack thereof, that lead to increased emissions levels. Regular maintenance includes checking and replacing oil, ensuring the fuel system is clean, monitoring the exhaust system for leaks, and replacing air filters. When these aspects of vehicle maintenance are ignored, it can lead to inefficient engine operation, causing the emission control systems to function improperly and produce higher levels of pollutants.

While the other options mention valid activities, they do not specifically align with the direct impact on emissions that results from neglecting essential vehicle maintenance. Proper maintenance is crucial for optimal vehicle performance and emissions standards compliance, highlighting the importance of consistent and thorough care for a vehicle to ensure it remains within acceptable emissions limits.