Hi guys, new guy here. Running into some serious misfiring issues, hoping to get some advice.

I have a 2004 Monte Carlo SS Dale Jr Edition and I have installed the ZZPerformance Stage 2 kit with a 3.6 pulley. At first, I installed the 1.0 PCM and just the intake, and everything ran perfectly, much better than stock. The next day I installed the Autolite 104 plugs, 180 thermostat, 3" downpipe w/ cat, and the modular pulley system with the 3.6. It idles perfectly, runs great under light load, but the second you give it hard throttle, it misses like CRAZY. Scan shows cylinders 4 and 6 were misfiring, so I pulled the plugs and lowered the gap from .055 to .045. Also swapped out the OEM wires for brand new AC Delcos. I gained a little bit of my power back but I'm still misfiring...

I switched around the coil packs and cylinder 6 is still misfiring as much as it was but 4 cut back quite a bit. It's still missing, but not nearly as often as before. I decided this morning to bite the bullet and I picked up 3 new OEM style coil packs, and have just installed them now. I haven't had the time to test drive it yet, because I am waiting for a quikweld fix to dry. I found a small vacuum leak on the hose leading from the S/C bypass solenoid, so I replaced the hose and waiting for the reglued fitting to dry. I can't imagine that this was causing my misfire though, as if my knowledge is correct, it only effects boost.

If these packs don't work, does anyone have any ideas? I am completely stumped. I am kind of in panic mode as I need this to be running correctly by Monday, as I start a new job and need a reliable car. Any help is greatly appreciated. A big thank you in advance as well.

-Myers

 

Sometimes, fuel injectors are the problem. But, Im having issues very similar to yours as well...

 

Start it up in a pitch black situation at night, no moon. See if you can see arcing.

 

Thanks for the quick response guys. Got it working perfectly. The coil packs help significantly, but it was still missing. I started thinking that my specific car just wasn't liking the Autolite 104s, or they were bad somehow. picked up a set of NGK TR55s and everything works perfectly. 10x better than stock!