I have a 2004 3.8L that i purchased 6 months ago, and just recently i've been having problems getting it to completely start. The first time was when i was just getting out of work and it just finished snowing and the outside temp was in the 20s. I tried to start it and it felt like it wanted to start but wouldn't. (it has started at other times at below 0 temps) So what i ended up doing was reving the engine while trying to start it and started right up but as soon as i let go of the gas it died. I tried it again the same way but this time i pushed the gas about 1300rpm for about 30 seconds or so while running and took my foot off and it stayed on. My first thought was that there was some water in the tank from the snow so the next day i put some HEET into the tank. After a few days it never did it again until the same thing, the temp outside was in the 20s (but it did not snow) and sounded the same trying to start her. So i started her the same way as before and again it worked. Of course there is something wrong, but i need some ideas of what it might be!

 

My first thought would be the idle air control valve circuit. At 29 degrees it should be allowing air to bypass the throttle plate to support the higher idle till warm up. Pressing the throttle does the same.

Odd though that it has started at 0 degrees. has it done that since the problem at 20 degrees?

 

I agree with Kyle William Park, its most likely the IAC valve.

 

Belairbrian-yes it has. Now that it starting to warm up it hasn't done it since.