Dirt and gum accumulation is the most common throttle body problem. The buildup constricts the air flow and the smooth movement of the throttle plate inside of the throttle body. This causes the engine to idle roughly, stumble during initial acceleration and possibly stall.
Internal combustion engines run primarily on air ? about 15 parts air to one part fuel by weight ? so proper air flow is critical to smooth engine operation. Clean the throttle body only with the appropriate throttle body cleaner and tools. Some throttle bodies have a special coating designed to help avoid buildup, and improper cleaning may damage this coating. Never clean a vehicle's throttle body with the engine running, because most cleaners are highly combustible.