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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
 

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I had multiple misfires from copper core autolite plugs. I tried several sets. I have had good performance from autolite double platinum. Another great plug is NGK. Just make sure you run at least 1 colder heat range.

You need to check to see if your fuel pressure regulator is ok. Unplug the vacuum line and check for gas dripping or a strong gas smell.

You need to be able to SCAN your engine for KR-knock retard. You also will need to know if you are running too lean. Do not get on your car without knowing if you are lean. The O2 sensor bank 1 should read at least 920mmv. Preferable 940millivolts at Full throttle.

The FIRST mod you need to do is a performance Fuel pump. The stock pump is very marginal. If you go lean with this engine...detonation=mushed pistons

Best of Luck
 

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When this happens to the guys here in OZ, they usually re gap plugs to 1.0mm or 0.9mm which is your 35-39 thousandths. So maybe try a bit smaller again than you currently have ?

Cheers
 

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I have gapped the Autolite copper core race plugs at a tight .040 because I was running NO2 then. I still had multiple misfires on 3 new sets of plugs.

The double platinum Autolite plug is superior partly because of the non-conventional way that the ignition works. The plugs fire from electrode to ground and they also fire from ground to electrode. Obviously there are other great plugs like NGk, but that has been my experience with the copper core plug. I doubt if it had anything to do with a 3 cold heat range.
 
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