I hadn't started my car for about a week and a half. It's been cold, high of 28 F today. My car cranked a little weaker but started up ok. But then I got this strong pulsing sound from engine and exhaust, every 5 seconds or so. I was going to shut it down but then it started to subside, only one pulse every 10 seconds. After about 5 mins it finally stopped and sounded normal. This was definitely a big noise and grabbed my attention. I know people drive their 8's in all kinds of cold weather including Canada with no problems. I've popped the hood and checked my plug wires, their on tight. Car is an '05 sport, 6spd, stock with 1200 miles. It's had 4206f done and been running fine since Nov. Anyone have any ideas? Thanks

 

I've heard mine make extra noises on start up before when the weather was colder. I don't know about "big" noise though..

 

When I started mine the other day at -10F I was making strange noises but only cold weather rattles from the car!
The car started with a run up to almost 4000 RPM for a few seconds before settling down. No strong pulsing sound though.