2000 accord ex check engine lite cause?

any idea why the check engine lite is on in my 2000 accord ex , the car hass
been running rough at lower rpm and acted like it wanted to die. the code
showes that car is miss firing on cyc 2, 3, 4. the distrributor was replaced a
bout 2000 mi ago due to an oil leak. I have had this car since it was new vry
well maintained only 150,000 mi