Hey everyone.

Got a few codes that I'm wondering if anyone could give me some clarity on whether I should be worried or not. First of all it's important to note that my car does not have a catalytic converter, and it also has a custom air intake system. The car backfires like crazy when I have the trifecta tune enabled usually around 4,000 rpms.

Thank you for your time!

 

backfire like crazy? like a machine gun? if that's what its like its most likely injector seal going out or gone.

 

It depends on if I try to go over 4,000 rpms. If I try to push it over 4,000 rpms, then it backfires a ton and my check engine light will flash for about 10 seconds and then shut off.

 

Ok try this try going over 4k rpm while staying out of boost, if it doesn't do anything then it's probably ur boost pressure at 4k rpm that is causing cylinder pressure to be high enough to blow past injector seal. I has similar , it was fine till 20 psi, after that it backfired like crazy. Got misfire in cylinder 4, never a light though. Try that.im sure it's ur injector seals. Sounds like it anyway

 

Check ur spark plugs as well to make sure there is no oil on them and that they are good.

 

Hey tom,

I tested your first theory on my way home from work today...I got up to about 100 mph in 3rd gear with no backfiring. I slowed down to about 50 and floored it and it started backfiring pretty quick. It seems like when the boost goes up to 20 pounds it starts backfiring pretty quickly. I was also able to replicate this issue in 2nd gear, could easily do like 60 in 2nd gear if I didn't stomp on it

 

yup that's ur injector seals then. get urself a new intake manifold gasket and injector seal kit from create engine depot and ull need the injector seal tool. I think there is a how to on how to do it. and change those seals. that will solve ur backfiring problem.
u should read through this, I think ull learn how to change the seals from it. ill give u links to parts and tools u need to do the job and a valve gunk check while ur at it.
https://www.cobaltss.net/forums/2-0l...r-seal-266006/

here is injector seal tool ull need. id advise u to look for it on ebay or amazon for cheaper price. u can find it for less than 100 usually.
Kent-Moore EN-48266 Injector Seal Installer / Sizer (EN48266)


first ull need this
https://www.cobaltss.net/forums/how-...nifold-304187/



Ecotec Intake Gasket LNF 12589366

LNF Fuel Injector Seal Kit 217-3425 12633374 12653395

this one u apparently need to change once u take it off. its the high pressure line from fuel pump to fuel rail.
Cobalt LNF Fuel Pipe 12615401

and if ur doing that u may as well change this to. its the pvc valve inside the intake manifold. easy to take out and replace.
LNF PCV Valve 12589440


while u got the intake manifold off. take a look at ur valves and see how gunked up they are. if its bad, u may want to walnut blast them. check out this how to if u need to do this.

https://www.cobaltss.net/forums/how-...emoval-304188/

of course if u still have warrenty, flash back to stock and take it in and tell them what u think it is.

 

Hey guys...I hope it isn't too terrible to necro this thread...but I feel like it is worth it for anyone in the future that may have this issue. I just got the SS out of storage from being in there all winter and I am headed up to ZZP tomorrow to get some work done... I am changing transmission fluid, oil, and spark plugs.


The attached pictures are what I found in the car for spark plugs... The gaps range from .030 to .052... If you look at the picture of the single spark plug you will also notice the top part of the plug is literally chipped off. Also you will note that these are not the NGK iridiums... autolites... wtf.

 

If this is an LNF you need to be running stock plugs. No question about it.

Stock gap or slightly smaller.

ZZP will tell you the same.

 

stock plugs my good sir, put in stock plugs

 

I got the stock plugs in there now! It is in fact an LNF too! I took it up to ZZP 1 day after I replaced the spark plugs and now its a monster! It pulled 300 HP and 337 torque on Friday after Matt dyno'd it! She should be really happy witht he stock plugs in there now...Don't worry she will have stock plugs for the rest of her life because I don't plan on selling her haha.

On a side note...I do have a p2261 CEL now after I got all the work done by zzp :/. Anyways I hope this info helps someone else searching out there with this problem! Change those spark plugs!