For the record, this is my girlfriend's car, and my experience is all working on larger American cars. Nevertheless, here's my problem: The car is a 2000 2-door EX, about 50k, and has always been serviced properly as far as I know. Today I had some trouble getting it started; it sounded like the starter was working weekly, and then it died. Started up fine on the second try. Rolling into a parking lot, it died on the way into my space. Got it started and drove home, but it died once on the way while I was stopped at a light. If I take my foot off the gas, the tach jumps quickly down to zero, and the car dies soon thereafter. The battery seems to be okay, as the lights and windows still come up after it dies, although the windows do go up noticeably slower than usual. It is pretty hot today, for what that's worth.
I read some of the other threads that suggested checking to make sure the fuel pump was coming on before starting, and it certainly sounds like it is.
Thanks in advance for any advice.

 

Is the CEL ON?

Is the charge light (battery symbol) staying ON or flickering?

When you turn the ignition key to START, does the starter strain to crank the engine slowly prior to the engine firing? If so, carefully clean the battery terminals and connectors and the battery ground wire connected to the frame. Also consider having the battery and alternator tested and the battery charged at your local auto parts store. This is often a free service at the major chains.

 

It drives OK once it is going? In that case I suspect a clogged or stuck idle air control valve (officially called the Electronic Air Control Valve -- EACV). Were that the problem, you should be able to step lightly on the gas pedal to give the engine some air, and it should start better and also keep running at stoplights.

 

Thank you for the advice thus far. I went out and played with it a little more, and right now it seems to be doing fine. It's a little hesitant to start, but the tach no longer jumps down to zero when I take my foot off the gas. No lights are on, and it drives normally. I still want to know what the hell was going on, of course, so I'm going to keep playing with it. The battery connections look alright, but I'll try to take it in tomorrow to have the battery and alternator checked.
Is there a good way for me to test the air control valve? I know how to do it on a Ford but have no idea on a Civic.
Does the fact that the problem went away suggest anything? It is noticeably cooler today, for what it's worth.