I already replaced the flame sensor thinking that was the issue...same problem fans starts first and the sparking goes crazy pilot lights on for just 2 o3 seconds...anybody out there who knows about lennox HELLLLPPPP PLEASE.!!
Place the sensor in a better position in the flame. Make sure all wire connections are tight, including ground wire. Does the control board have a ground? Is the high voltage have a ground that's connected?
Make a call to a good service company. That furnace is around 30 years old and you want a safety check every year to make sure the heat exchanger isn't cracked. They can tell you what's wrong while they're there inspecting the thing.