Cold problem

[Argeo]

I am suspecting the fuel accumulator but please let me know what you think. When I start the car it starts great. But for the first 10 - 15 mins (while cold), if I was to put the car in neutral while driving and take my foot off the gas the RPM's crash to zero. When the car gets warm, it does what it should where the RPM's drop a bit then slow until it hits about 800 RPM's. Sometimes when cold the rpm's will drop to zero, bounce back up to 1500 or so a couple times and then die. That indicates rich right? Any ideas. No backfires and like I said, when warm it runs great. I also had a problem a few weeks ago, where I drove around for a while, park it and came back 30 mins or so and it wouldn't start. It cranked, just wouldn't start. Well let the car sit, and sure enough it started when cold. This problem is not reoccurring though, but is it a sign?

Any suggestions?