Can IAC valve cause engine to run lean and stumble?

Yes, a malfunctioning Idle Air Control (IAC) valve can cause an engine to run lean and stumble. The IAC valve regulates the amount of air entering the engine at idle, and if it fails or becomes stuck, it may allow too much or too little air, disrupting the air-fuel mixture. This imbalance can lead to symptoms like rough idling, stalling, and hesitation during acceleration. Proper diagnosis and repair of the IAC valve can help restore normal engine performance.