I'm new here to pontiac bonneville club. I have been having some problems with the car. It doesn't want to shift gears, it idles rough, and just has a lack of power. The check engine light would flash whenever I gave it power. I had an OBDII scanner hooked up and it read p0306 which said cylinder 6 misfire. I recently (4 months ago) replaced all the spark plugs and all the wires. I checked cylinder 6 and it was fine. No cracks or anything. I pulled spark plug #3 to compare the gap with #6 and noticed that #3 had 2 spider web cracks in it. Replaced it and put 6 back in. Still runs bad. So next I checked the coil pack which connects #3 and #6. And it was fine. Same ohms as all the other coil packs. So now where do I go from here? What else could be the problem?
Thank you.

Check fueling, you might have a leaky or clogged injector.

Also make sure the Cat isn't clogging up. If you were leaking unburnt fuel into the cat for a long time, it could degrade and cause a loss of power feeling and odd shifting.

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CSC Powered 2000 Monte Carlo SS - Project Car
2013 Camaro 1LS - Daily Driver
1968 Camaro SS - Show Car

I had this problem about a year ago and it was a bad cat. I replaced it and everything was fine until about 4 months ago, when I had a misfire in cylinder 5, spark plug was bad. That's when I replaced all my spark plugs and my wires. But thanks, i'll check the fuel injectors next.

What cat did you replace it with?

If it was a cheap high-flow they can go bad pretty quickly. If it was expensive OEM quality, you should be fine. But if it was a cheap one I would still get it back-pressure tested

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CSC Powered 2000 Monte Carlo SS - Project Car
2013 Camaro 1LS - Daily Driver
1968 Camaro SS - Show Car

What brand plugs and wires did you use? Did that solve the problem for a while, or wasn't it occurring then?

Try swapping the 3/6 coil with another, and see if the problem follows the coil. If not, swap the #6 injector with another. Also, make sure the #6 plug wire is routed away from the wiring to the O2 sensor.

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*Gone, but not forgotten* - Black 2000 SSEi, HIR Headlights, Angel Eyes fogs, 3rd brake light overlay, hi-flo cat, 180 degree thermostat, HS 1.9 rockers, LSx yellow springs, Intense FWI, PCM, shift kit, push rods, and 3.4 Pulley. ZZP Power Log.

I don't remember what brand wires I used, but everything has been fine since I did. Last time, cylinder 5 was misfiring. Replaced it and all the wires cause I broke one when removing it. Until recently the car ran fine. The code now was for cylinder 6. Checked the plug and it was fine, but checked plug 3 and it was spider webbed so I replaced it. So all my plugs are fine, my wires are fine, I recently replaced the coil pack which connects the wires from cylinder 3 and 6. The car runs a lot better, but it still has problems wanting to shift, but it's nowhere near as bad as it was. And I checked the fuel injectors and the rail. All good. So now i'm going to have the cat checked out. After that, if it's fine, I guess i'll have to take it in cause it's probably an electrical problem. Heard that bonnevilles have lots of electrical issues.