HELP with misfire issue
 

I went ahead and just copied the post I put up on Camaro5, in hopes for more opinions.... anyways, please help out if you can.

I am looking for some help with my 2012 ZL1 and hopefully someone can help out. Heres just a generic, quick list of mods, then Ill get to my issue.

2012 ZL1
6spd
Cam/cam kit
Full exhaust
clutch
102mm TB and ported snout
Nitrous Outlet System
Tune(ovbiously)

Car was running flawlessly, crisp, responsive ect.... One day about 2 weeks ago, I noticed the car started to feel more sluggish and not as powerful. As a couple days went on, I could feel the car was stumbling and misfiring and not to mention, my wideband now will bottom out on 10.0(PIG RICH) when it used to hover at 11.0-11.2 at all times.... As I have owned many high HP cars, I decided maybe it was time to change the plugs. While I was doing it, I wanted to replace the wires too. Either way, that didnt fix or help the problem.

Completely driving normal like a grandma, its not really too too noticeable but as soon as I remotely put any load on the car, its starts sputtering bad. So at that point, I decided to scan the car while driving under load so I could start my diagnosis. Came up with a crazy cylinder 3 misfire. Just 3-4 seconds of rolling into the throttle, misfire counts hit near 100 on cylinder 3.

So first thing I did was swap coils. Still stayed on cylinder 3 misfire. I then pulled the valve cover to see if maybe a valve spring broke, or maybe atleast one of the dual springs were broken. Visually looks intact. I tried to push down on the spring as hard as possible and couldnt budge it. With that being done, I went ahead and did a compression check and then followed it up with a leakdown. Both passed with flying colors.

Being stumped, I put the car back together, then decided to swap a couple injectors. Put it all back together and the cylinder misfire is STILL on cylinder 3

Please if anyone has any other tricks or opinions, please let me know. Any and all advice is greatly appreciated.

JASON

Did you try swapping plugs or wires? Could be a plug issue

Sounds like a plug wire

plugs (loosened up, cracked ceramic, etc), plug wires (not fully snapped on), dirty maf sensor, etc..

How much fuel rail pressure are you getting?
I've seen misfires keep popping up before and it would be the rear cylinders because the fuel pump couldnt keep up with the commanded power level. But is usually would start to misfire on number 4 and work back to 6 through 8.