Car sputters on startup when it's cold outside.
 

This just started happening when the temp dropped in Oct.--If my car is completely cooled down and it's around 50 degrees or colder, the engine sputters for maybe 5-10 seconds and then fires right up and runs perfect.

If the temp is above 50, it starts right up.

Could this be a coolant temp sensor? How do I check that. There's no SES lights on either.

**I'm pretty sure my car has a bad head gasket because coolant comes out of the radiator cap when I drive it hard. Could this be related to the starting problem? There's no coolant in the oil and I don't see or smell any in the exhaust on startup.

soooo how do you figure its got a bad head gasket if the coolant is coming out of the cap??

alot of guys up north have similiar issues....you can change the oil to the proper cold weather oil...(search)...replace the cap, and check back

Exhaust gasses are getting through the bad gasket into the cooling system creating more pressure than the system and cap can handle.

It's not that cold, only about 45-55 degrees right now. I would think 10w30w should be ok

try a 5w....the caps can go bad regardless because there under pressure....

If you have a custom tune you may have to check your settings for fueling at that low of an outdoor ambient. Thats too damm cold for me bro. But the radiator cap is a common failure point. If it does have a headgasket leaking then the sputter is coolant leaking into the combustion chamber and it takes a few seconds to clear it out after start up.

is the oil the only problem that can cause this, cause i'm having the same problems with an 84 celica, only when it's cold.