That's what happening to my 98 honda civic ex. I just saw little oil leak inside distributor cap edges. I know I have replace my distributor oil seal but I rather buy new distributor. I think this is what affecting my idle very low and my car stall out when I stopped at red light when idle. But I can start my car with no problem but it starts go very low idle when car stop . So oil inside distributor cap could be causing affect my idle very low about stall my car when engine gets hot.