I have a 91 Honda Civic DX, the engine surges around 500rpm (guessing) at an idle, seems to get worse in hot weather. Car runs great other than that but after reading other post I'm sure I will be replacing my master relay soon!
I have had times when the car would not start, I just cycle the key on and off until I hear the rely click then starts right up.

Thanks for any help

Rick Brown

Don't know your status... but here are some suggestions:
Tune up
*plugs
*air filter
*gas filter
*pc valve
*check for vacuum leaks... I think that model has a lot of hoses... if its surging at that low rpm there may be a leak at one of them
*check for damaged frayed cracked wiring while inspecting vac. Leak
*cat. And exhaust restrictions

Please, don't spend money on a NEW main relay. There are many posts here regarding civic starting problems. Civic's from late 80's till mid 90's all have mostly the same problem with main relay.

I have a Civic 91 DX and I've had problems starting when it was hot, and car wanted to die at idle. I'm slowly fixing stuff, and first thing I did was just resolder the main relay. There is a post here explaining how to do it. You just have to get it out (which is the hard part), resolder it (like a 15 minute work, and I've soldered only once in my life before that), and put it back in. Be sure to disconnect the battery before you start work. Also, check your ECU (under passenger's carpet, most likely) for error codes. Turn the key to II (before cranking it) and check ECU for LED blinks. 16 blinks should tell you that you have a problem in Fuel Injection System, and main relay is a part of it. Once you resolder the relay, and put it back in, connect the negative battery cable back, and check for 16 blinks again. My ECU didn't blink any more when I was done. Also, it's been a week now, my brother and I myself were really testing the relay, trying to start it when it usually wouldn't and its working flawlessly.

Anyway, let us know if this helps.

Kresho