Toyota 2.5 Dynamic Force rough cold idle: carbon on the intake valves, and why it is rarer than forums say

The A25A uses both port and direct injection precisely to keep the valves clean. When idle roughness does appear, it is usually something cheaper.

Direct-injection engines without port injectors coke their intake valves because no fuel ever washes them. Toyota's D-4S adds a port injector per cylinder that runs at idle and light load, which is exactly when deposits form. The result is an engine that stays clean far longer than the turbo fours it gets compared with.