Why

@@sparkyggs4019 When you rev your car when it's cold, it causes your engine's temperature to change abruptly. That puts stress and unnecessary wear and tear on your engine

@@sparkyggs4019 Metal expands when it heats up. Therefore, engines are designed to be within spec at operating temperature and not when they are freezing cold. When the engine is cold, all of the metal parts are just a tiny bit smaller than they should be causing excess wear. On top of that, engine oil gets extremely thick in low temperatures causing it to flow more slowly throughout the engine. This prevents certain components in the engine such as the valve train from getting proper lubrication during the first few seconds after starting.

Old comments The pcm is actually program to idel higher when cold to warm up the engine faster. The reason you don't rev on cold start is, cold oil velocity is lower Than hot oil so it take longer to circulate throgh the engine, but your in the clear after about a min or two

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