hard miss on 2004 Pontiac Grand Prix GTP

when cranking my car it has a really bad miss. the code reads random/multiple cylinder misfire. I just replaced the plugs and wires. I also tested the coil packs to check the firing and all produced a big blue spark like they should. what is causing this to occur?

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1 answer
Did this start after you installed the plugs and wires? If so there may be a bad spark plug or you may have crossed the wires. Recheck your work.