What might indicate a problem during the inspection of the vacuum booster?

The situation described indicates a potential problem with the vacuum booster system, which is crucial for the proper functioning of the braking system. When the engine starts, the vacuum booster assists in applying additional force to the brake pedal, making it easier for the driver to engage the brakes. If the pedal shifts slightly when the engine starts, it can suggest that the vacuum in the booster is building properly, but if the movement is excessive or irregular, it can indicate an issue with the booster itself or a potential vacuum leak.

A braking system that is functioning properly should allow for smooth operation of the brake pedal with minimal movement upon engine start. Thus, the slight shift in the pedal during engine startup can be a strong indicator that further investigation is required to assess the integrity and function of the vacuum booster, as it may not be providing the expected assistance.

Other signs, such as brake fluid leakage, would indicate issues elsewhere in the braking system, while a hard pedal when pressing could indicate a failure in the booster, but the pedal shift specifically points to the immediate evaluation of how the booster operates within its intended vacuum system.