For about two years, I searched the Internet for a solution to my automotive problem. My 1995 Subaru Impreza would cold start just fine. But if the outside temp rose above 70 degrees (F, duh), or if the car had been driven long enough to warm up then stopped (like, at a store), I had something like a 1:3 shot of it starting. Did all kinds of searches on Subara warm start problems, etc., but never found anything until recently.
I ran across a few usenet postings and things in website-hosted BBs that led me to believe I had either a bad camshaft or crankshaft sensor. I ordered them, and one our friends kindly installed them for me whilst I whittled away at the horrific, criminal default security setting of his Windows XP Home Edition-based computer. Since the sensor was put in, I've had eight good starts under the suspect conditions. If my initial 1:3 estimate is anywhere near accurate, there is about a .01% chance that I could get eight good consecutive warm starts, so the math tells me that the car is either fixed, or that I've wasted a rare probability wave on a stupid car instead of on something nice like a lottery ticket. Oh well.
So, for anyone who has the same problem as I did, and can't find it on Google, until now:
1995 Subaru Impreza warm start problem.
Replace the camshaft and crankshaft sensors. Replace the coolant temperature sensor, too.
Why didn't I take the car to a dealer? Because I regard them as little more than thieves. I've had some really bad dealer service experiences. Why did I let it go this long? It didn't hit the 1:3 ratio until this summer, and well, I could always catch it in gear. I could easily envision a $400-500 "investigation" into the problem. Why fix it now? It was getting out of hand. And, I'm going to need a reliable car if I'll be driving to Virginia a whole lot in the near future.
So, I fixed it for $60 in parts. God Bless the Internet.