310T Truck and Coach Technician Certification Practice Exam

Frequent stalling during idle can be indicative of air intake issues in a diesel engine. When the engine is not receiving the proper amount of air due to obstructions or restrictions in the air intake system, it may struggle to maintain the necessary combustion levels. This deficiency can lead to an imbalance in the air-fuel mixture, causing the engine to stop running smoothly or stall altogether, especially at idle where the engine demands are lower.

While other symptoms can be associated with diesel engine problems, the direct connection between inadequate air intake and stalling is particularly significant. Excessive black smoke typically indicates a problem with fuel combustion, which could suggest a rich fuel mixture rather than an air intake issue. Decreased fuel efficiency can stem from various causes, including inefficiencies in fuel delivery, fuel injector problems, or maintenance needs, and may not specifically indicate air intake problems. Similarly, increased engine temperature could result from several factors, such as cooling system failure or improper fuel combustion, rather than solely from air intake issues. Therefore, stalling during idle most clearly correlates with problems in the air intake system.