[Jungle Jim]

I know this has been covered in the past but my problem seems different. I have changed plugs and wires with no change. I get no error codes on my EBDII reader. I did notice that the problem seems worse with the heater or air conditioner on when the cooling fan starts. Also the O2 sensor output is a sine wave when it is running smoothly but the wave form distorts when the engine stumbles. I don't know if the O2 sensor is just reporting what is happening or is the cause of the problem. Also when the idle is held above 1000rpm it does not stumble. I am thinking it may be the coil or the O2 sensor. Any help would be appreciated.

Thanks,
Jim