87 Accord Starting Problems

I have an 87 LX (the carbureted model.) In the past few weeks i've been having some trouble starting my car. The weather has just gotten a little colder and dryer, but I don't know if that has anything to do with my problem. Typically, I'll put the key in and turn the ignition and the engine will start just fine, idle for about 15 or 30 seconds, and then just die. When I try to start it again, it sounds like maybe one or two of the cylinders aren't hitting, and this whitish smoke that smells like gas pours from the exhaust. I also have to keep the accelerator depressed in order to keep it revving. It sounds and smells a lot like a motor boat. I've only had this car for about five months, so I'm not very experienced with it. At first I think I was probably just flooding the engine, but now I'm not so sure.

When the engine can finally rev on its own (which didn't happen this morning), it typically runs pretty well. I've been getting ~25-27 mpg.

Another symptom that I've been having, which may or may not be related, is that the engine has been idling a little high recently. It typically idles at around 1000rpm, but lately its been switching between 1000 and 1500. I've found that when the engine is warm, if I gun it in idle it'll usually drop back down to 1000.

It seems to me that the problem is probably either the spark plugs or else the fuel mixture, except that I would expect those things to reduce my gas mileage. Any ideas?

Thanks for the help.