bad misfire need help

[mazdanut]

I own a 2004 Mazda B3000and I'm having a good bit of trouble figuring out why I have a weak spark out of my first coil on the module and good spark on the other two. I have replaced the coil three times, replaced plugs and wires and fuel filter. The truck wont even spin a tire in gravel. No modifications have been done to the truck other than the cats being cut off and the reason they are off is because they were almost plugged upand made the truck lose power in upper RPMs. Any advice would be greatly appreciated. Thanks

 

[mazdanut]

Could the cam or crank angle sensor cause this? Or the cats being cut out?

 

[adsm08]

Well nothing you have listed so far points directly to a bad part. The weak spark may be what plugged your cats to begin with.

There are really only two things left that I can see causing your issue, a bad wire to the PCM, or a weak coil driver in the PCM.

All 3 coils shares a primary 12V hot and get fired by individual drivers in the PCM by being grounded, so I'd look at the ground side of the circuit now.