It's getting cold here in the greater Toronto, Canada area, and some differences I've noticed in this engine when cold vs. my older late 1990s to mid 2000s engines are listed below. You guys notice the same in your IS350s?:

1. It revs very very high after cold start up, like sometimes up to 1,750rpm
2. Some engines get coarse when cold revving. This one remains very smooth and feels free revving even when you're driving it cold
3. When just started cold a few minutes ago, and idling at a red light, it revs at like 1,000rpm. You really need to keep that foot on the brake pedal because the car feels like it wants to run away, or a dog pulling ahead on his leash. I figured this is deliberate programming so the engine can get to normal operating temp ASAP
4. The handling is still pretty nimble even with narrower snow tires. I have Pirelli Ice Zero FR on 17" F-Sport replicas. I didn't go crazy on the on-ramp with the cold, but the car still felt very stable and inspired confidence

 

What are your cold start ambient temps?

 

High 20s and cooler.

 

Cold start idle really depends on the ambient temp that the vehicle is sitting in.
One winter when it was effing cold, at least -25C, I jumped in a 2004 Corolla and fired it up, the revs jumped to 2100 RPM instantly.
And yes, it is to get the vehicle to normal operating temp as fast as possible.
Contrary to popular belief, the vehicle will actually warm up faster if driven, opposed to sitting an idling.
Usually a minute idling in very cold temps is good enough, and then driving gingerly until it gets up to temp.
Plus, 15 minutes of idling isn't good for the engine internally either...talk about buildup.

 

Mine's the same way - always smooth, but idling fast, when it's cold. As for the tires, my 225/45-17 Dunlop Winter Sports are noticeably "squishier" than the 225/40-18 (square) Michelin Pilot Super Sports that I run in the summer, but still OK.

 

This morning, it was in the 30's. My car was spinning at around 1000 RPM at a red light, which is higher than usual for sure. I turned the HVAC system off, and suddenly it dropped to 600 RPM, even though the coolant temp was still a bit low. So, I think multiple factors are affecting the idle engine speed - possibly also trying to warm up the air in the HVAC system as well as the engine oil temp.

 

My 2008 GS350 will not move when temps are below 0.. Its almost as if the car is in neutral when its actually in gear. I have to warm it up for about 5 to 10 min. then it will start to roll.