87 civic sedan, idles fine until engine warms up and then it surges nonstop and it's gradually getting worse.any ideas what this would be?

Carbureted or fuel injected?

carburetor

Off the top of my head, it could be one of 4 things:

1) Vacuum leak. Cover up the intake on the carb. if the motor dies it's ok, if it keeps going you've got a leak. To track down the leak spray carb cleaner around base of the carb and around the intake manifold, if the idle evens out, you've found the leak. Also check your hoses.

2) Bad carb. Squirt some carb cleaner down the carb to clean it out. Also squirt some carb cleaner around it to clean off the carb body and linkage. Might be time for a rebuild.

3) Bad fuel pump. Check your fuel pressure to find out if it's good or not. Also check voltage to the pump.

4) Bad O2 sensor, Check Ohms.

I'm leaning towards a bad O2 sensor simply because it happens when it's warm, but it could also be the low idle circuit on the carb. Without knowing the condition of your motor, it really could be any of these. Check for vacuum leaks first simply because it's cheap and easy to do. If that doesn't solve the problem then check out the carb, fuel pump, oxygen sensor, then fuel pump. Also just to be sure, check your battery and alternator while you're at it.

thanks for info lxndr