Hello all,

I am having some real trouble with my 2009 cobalt ss/tc. I have the P0302, P0303 and P0304 random misfire codes going on. I have also noticed a considerable loss in performance. The check engine light also blinks quite a bit. I have changed the plugs (gapped to correct length) and changed the coil packs. I really need some help on this as I cannot find any other forum or help page on this issue. Also my mods include a SPEC lightweight flywheel, Injen CAI, Stage 2 KY clutch, hahn 3" exhaust (not sure if the mods will help in diagnosis).

Thank you so much in advance.

 

u get these codes all the time or just when u do a pull or what? also stage 2 clutch? why didn't u just stay stock if ur gonna put a stage 2 on there?

 

I have the issue at idle most often. When I regular drive it does it sometimes but not often.

Also, I burnt my clutch out and decided to get a stage 2 for future mods and a trifecta tune. Which after this problem is fixed I will be installing.

 

Did it start right after the clutch and FW install?

 

Yeah does anyone really run the lightweight flywheel anymore? I thought it caused more issues than HP gained.

Can you feel the misfires? or are the phantom misfires?

 

I can feel them when idling most of the time. But when driving I cannot. Also I am not sure if they happened right after the fw and clutch install. I installed both of them in August. And the reason for the lightweight FW is that it is cheaper than stock FW. I burnt my stock one lol.

 

Will a dealership be able to tell me if it is the flywheel or not? I have read that it might be an issue, but like I said, I can feel the misfires sometimes so they aren't all phantom. I just don't want to waste money on the dealership if they can't tell me what's wrong.

 

The dealership is going to tell you it is the aftermarket parts, take your money and say too bad.

 

Well ****. How do I fix this!? This problem is consuming me lol. Could it be any of the sensors?

 

You need to log the car and have some one that knows them look at that log.

Flashing MIL means it is ignition related tho.

 

Sorry for the ensuing stupid questions. I am still learning. How do I go about logging my car.

 

Did you look up the codes and see what the possible causes for each one are and look there first?

 

I looked on forums and such. The fact that they are random misfires points to a lot of issues not just a few, at least from what I read. I was really hoping someone had the same problems and could tell me without having to spend a whole bunch of cash, I am on that college budget haha.

 

I have only had a p0300 and it was fuel related. It was new injectors on a LSJ and the tables need adjusted some for it to clear up.

A log would help tell you if they were real or not. The flashing makes it ignition related.

Search for the code descriptions and post up the possible causes for each one.


You sure that this didnt start when the FW went in?

 

Are you sure everything was tighten back down after the clutch install? Could be a bad ground causing issues or a battery that is about to crap out. Does it misfire when you go WOT or just idle and light load? Also how many miles are on the car?

 

Did you install the clutch? Maybe an error in wiring.

 

Check for a minor boost leak

 

A week seasoned mechanic installed the clutch. So I'm sure everything was done right on that end.

As for the boost leak, wouldn't I see the psi drop if that was the case? But, how do I check for one?

Also the more and more I think about it, the more I'm sure it happened after the flywheel was installed. Does my car just need a tune?

Thanks everyone, you all have been great thus far!!!!

*well seasoned mechanic

 

And it misfires when I idle and light load. As of late I have been posting real attention to the car in idle... And it seems almost all of the misfires are phantom misfires

 

Take the brake booster nipple out of the IM and use a borescope to look at your intake valves. Good chance you have coked valves.