This problem is beyond my knowledge of cars. When I turn off my car and come back to it in 1-2 hours and start it, it starts acting wierd. It idles normal for a second, then drops below 500, idles normal, drops...etc. When I drive for a second and push in the clutch, it continues to do it and usually dies. The other day it took a little longer to start it back up after doing this (which kinda worried me) After this happens I usually start it back up and drive the crap out of it for a minute or so. When I stop usually it decides to fix itself suddenly and idle at 1200 or whatever is normal for a cold idle.

This only happens when its been sitting for a certain period of time. If it sits for 10-20 minutes, its usually fine. If it sits overnight or while I'm at work, it works fine. Its only when it has enough time for the temp gauge to go all the way down, but the engine isn't completely cold yet. My guess would be some sensor is telling it the engine is hotter than it really is and screwing with its idle-and when it warms up completely it suddenly works fine. I don't know what sensor to check or where to start, really. Does anyone have an idea?

 

Oh, and I've replaced the spark plugs/wires, distributor cap/rotor, fuel filter, o2 sensor, and cleaned the air filter.

 

There is a TW (water temp) sensor that can get flakey. It will give the ECU incorrect information about the engine temp and can cause flooding or at least hard starting under the conditions you describe. Not sure about yours, but normally it's located just below the distributor. If you have a lot of time on your hands, you could connect an ohm meter to it and watch it during cool down for any irratic readings. Also, make sure there is no air in the cooling system.

One other possibility is the fast idle valve is dirty or otherwise acting up.

 

what car/year/miles? mods? what was changed/upgraded prior to the problem.. and how long ago?

 

93 del sol s (d15b7) with 90k miles, and just an intake. Its happened since I got the car about 5 months ago. But it just recently got to where the car would actually die. Like maybe a month ago. But it doesn't happen ALL the time. Its wierd. Also, my car seems to be a little quick to overheat. One day I left it running for about 20 minutes in 110 deg weather and when I got in the temp gauge was all the way up. No big deal, I cursed myself for being such an idiot, popped the hood and it went down within a few minutes. But a few weeks ago I came to a stop and idled for what seemed like 5-10 minutes on about a 80 deg night and it did it again. Hasn't done it since tho. And I have had the car die once before in extreme heat while I had been driving the **** out of it for maybe 1-2 hours.

Maybe the thermostat? I'll try replacing that tomorrow, but I don't know if the problems are related.