A vehicle's engine stalls frequently at idle but runs fine at higher RPMs. What could this indicate?

When a vehicle's engine stalls frequently at idle but operates properly at higher RPMs, this often points to the presence of a vacuum leak. At idle, the engine relies on a precise air-fuel mixture to maintain operation. A vacuum leak introduces excess air into the intake manifold, which disrupts this balance, leading to an inadequate fuel mixture that can cause the engine to stall.

At higher RPMs, the engine's increased air intake and fuel delivery can compensate somewhat for the imbalance caused by the leak, allowing it to run smoothly. This situation highlights the critical role that proper vacuum pressure and air-fuel mixture play in engine performance, particularly at lower speeds.