Hi thinkiam. You didn't mention it so I assume the battery is good, the connections to it and the starter are good and clean, and the starter motor turns the engine with sufficient power and speed. You also don't mention whether we are talking about extreme cold weather, or just normal cold which any vehicle should be able to handle easily. I assume also that it's just normal cold and the 4Runner simply isn't doing it's job. Believe it or not a heavy oil could contribute to cold start problems and some suggest a synthetic oil if your 4Runner doesn't leak too much. You also omitted plug wires. If the engine isn't firing, that's a potential source for problems. Finally (and again believe it or not) some small and independent gas stations will continue to sell summer blend gas in the winter. That gas, as a result, may not be vaporizing properly in cold weather conditions, contributing to your problems. Try a tank from a major national distributor and see. Yanevaknow ... Most likely you have some sort of weather-related ignition problem that could be anywhere in the chain and you'll eventually need a decent diagnostic done. Good luck.
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