When is an induction manifold leak in a turbocharged engine most likely to cause the mixture to become too lean?

In a turbocharged engine, an induction manifold leak can significantly impact the air-fuel mixture, primarily because the system relies on precise air intake to maintain the correct fuel-to-air ratio.

During taxiing, the engine operates at low power settings and typically at lower RPMs. Under these conditions, if there is an induction manifold leak, the engine might not draw the expected amount of air, leading to an increase in the proportion of fuel compared to air, which could momentarily cause the mixture to become richer. However, if there's a continuous leak, especially at low power settings, the amount of air entering the engine could be insufficient to properly combust the fuel, thus making the mixture leaner.

When the engine is at a higher power setting, such as during takeoff or climbing, the turbocharger's boost can help compensate for small leaks by increasing the air pressure in the manifold. This can help maintain the desired air-fuel mixture ratio. During cruise, the engine might generally maintain a stable mixture due to consistent operating conditions, which makes it less susceptible to the effects of a manifold leak when compared to the more variable conditions of taxiing.

Therefore, the likelihood of an induction manifold leak causing the mixture to become too lean is highest during taxiing