What can be a potential sign of a clogged air filter in an engine?

A clogged air filter can impede the flow of air into the engine, disrupting the balance of air and fuel required for efficient combustion. When the air filter is blocked, the engine may not receive enough air, leading to a rich fuel condition. This means that there is an excess of fuel compared to the oxygen available for combustion. The result can be incomplete combustion, leading to the symptoms characteristic of a rich condition, which may include rough idling, decreased fuel economy, and increased emissions.

In contrast, increased engine speed is typically associated with sufficient air intake and engine performance rather than a clogged filter. Overheating is usually indicative of cooling system issues or other mechanical failures, rather than air intake problems. Excessive smoke could indicate other issues, such as burning oil or engine misfiring, rather than being directly linked to a clogged air filter. The rich fuel condition directly reflects the consequence of insufficient air reaching the engine, making it the most appropriate indication of a clogged air filter.