I have recently discovered that my truck is misfiring. I do know that the catalyst system on my passenger side is out but the mechanic said I need to fix the miss fire before replacing it to prevent it from happening again. When it first started happening I was on the freeway and it started stuttering then when I had to stop at a light it died and my check engine light was flashing. After that I replaced all of the spark plugs and wires. But the problem still continues just not as bad. I can't even really feel it but my gas mileage is poor and when mechanics hook their computer up to it, it says random miss fire