Which of the following is a characteristic of an IDI engine?

An IDI (Indirect Injection) engine is characterized by the use of glow plugs for starting. This type of diesel engine has a separate combustion chamber where fuel is injected indirectly. The glow plugs are crucial for preheating the combustion chamber, especially in cold weather, to facilitate the ignition of fuel. When the engine is cold, the glow plugs heat up the air in the pre-combustion chamber, ensuring that the diesel fuel ignites more easily once injected, leading to smoother starts.

The other characteristics mentioned do not accurately describe an IDI engine. For instance, a direct fuel injection system is associated with DI (Direct Injection) engines rather than IDI engines. The statement about relying on induced airflow for combustion would more accurately pertain to engines with specific induction systems, and saying that IDI engines do not have an exhaust system is incorrect, as all engines are required to have exhaust systems to manage emissions.