Okay so here's the deal guys. I have an 06 SS/SC with 2.8 injectors, tune. About 3 weeks ago my car threw up a check engine light. Had guys at Autozone run the codes and found a random/multiple misfire, and a coil C malfunction. Had all 4 spark plugs replaced with NGK Step 2 colder plugs, and a full synthetic oil change just to be safe. Continued to get consistent check engine lights reading Coil C Malfunction. So I ordered a coil from Chevy ($82.85) the black piece that goes ontop of the spark plugs. So when it came in I replaced it. Check engine light didn't come back on, but still is misfiring. I can hear it in the exhaust when it misses, and also it bucks lightly when I'm driving at low RPM's, but seems to be less present at high RPM's under heavy load. Any ideas as to what could be causing it? I am clueless at this point as to what it could be. Hoping not to have to replace my entire ignition system...$$$.

Also...my bumper to bumper warranty expired at 36k miles. But the previous owner of my car purchased a powertrain warranty through 105k miles. What is covered under powertrain from Chevy? Clutch? New motor? Supercharger? Tranny? Any and all help would be greatly appreciated.

Thanks.

 

anyoneee

 

what size injectors are you running?

 

do you have any cooling mods? heat soak will do it, it does for me if i sit at idle long enough.

 

There's your answer right there! 1 step colder is the max you ever need to go.

 

no cause it's still misfiring like a mother. AFTER i replaced the plugs along with the originally misfiring coil (Coil C) it still misfires. i went and had the codes re-read, and it is still misfiring on cylinder 3 and coil c malfunction. so i took the coil out and took the plug out...plug looks good, coil seems fine. I HAVE NO IDEA. only cooling mod i have is the airbox mod with aftermarket filter.

and i'm running siemens 60lbs-ers. but it has a dyno and tune from SMG.

 

if your running a 2.8 u need to get a H/E also check in to Option B because u can do it yourself fairly cheap to help aid with the cooling also get the 1 step colder plugs instead of step 2

 

but it's not like the step 2 are hurting the car. and also i know i need a H/E but i feel like that wouldn't necessarily affect the way the plugs fire or why cylinder 3 isn't firing right. it's not like my cars overheating or working too hard...i don't beat on my car at all. it's my daily driver. it has 80k on it...so i feel like this may just be a problem that comes with high miles...but again, i don't beat on it. and i replaced the part that was causing problems...so idk what else could be wrong.

 

2 steps colder is TOO cold.

 

maybe so...but it wouldn't cause a misfire on one cylinder and not the others. and especially not a recurring misfire on only that one cylinder.

 

My stage 2 car did this too , it would misfire at idle but never under load . It never would set a dtc thou. We tried just about everything and finally just assumed it was GM's tune. I have listened to tons of exhaust sound clips on SS/SC's and it seems like they all pop a little at idle .

The hesitation your feeling could be knock or your car pulling timing due to heat "MAYBE"..... or keep looking at ignition , could be a wire rubbed threw .

 

yea i went down to SMG today and had fred take a look. it threw up a P03503 code. which was a coil c main circuit failure. and also a random multiple misfire and coil c primary/secondary malfunction. called chevy, dropping it off in the morning for them to take a look. guessing they're going to blame it on the aftermarket parts and tune, and then charge me an arm and a leg to fix it/look at it. so...we'll see. and also..you're right, under load it runs fine...but only above like 3k rpm and i have to be on it relatively hard. but when revving at idle it doesn't just pop, it like...purr's up through like 2500rpm...and not a good pur...like a bad one. like a gurgley mess. it's bad.

 

I have the same problem, i had the coil replaced it still does it at first it only did it when i put the ac on which i can understand to much load, now when it was raining it just started to misfire like crazy i would be cruising and i'd step down a little more on the gas and it wouldn't go nowhere and misfire i put a load on it and it would go but once i got to 100 mph it would not go any faster i do not know what to do ? now it just does it all the time i don't get on it but if i do it misfires even when i don't get on it, i have no engine mods except tranny solid mount , torque damper , traction bars , strut tower bar, cool air intake, i get that bad purr as well it kinda vibrates when you rev it up to 3000 rpm. what the heck do i do to fix it if nothing i am just getting rid of it

 

dude, i have no idea. i brought mine to chevy for them to run a full diagnostic on it. i left it there over night, and when i picked it up the next day it was perfectly fine. like it doesn't do it anymore. all they did was run a diagnostic on it, and told me they didn't know what it was. so idk. i've been afraid to put my AC on lol. because now it doesn't do it on the highway, it sounds like it's misfiring when it's idling, but it's a smooth idle, and doesn't shutter or purr when i step on it in neutral. so i have no idea. i'm sure it'll end up coming back, but for now it's gone. ????

 

What's the gap on your 1-heat-range-too-cold plugs?

A lot of people gap their plugs too small on top of getting them too cold - this can cause all kinds of running issues.

 

Have you looked at the plug's? My car did that on a .040 gap with stage 2 . Then i closed it down to .035 and it cleared right up, I was amazed to say the least. The other things to look at are .....With a CAI .....I would pull the maf and clean it , it could be getting water on it or just plain dirty. The fender well doesn't seal up worth a **** and the **** comes right off the tire and runs down the inner fender right towards the CAI . I'd also check the fuel filter ..... might be starving for fuel . How many miles are on it?

 

I have the same misfire problem i am pretty sure its just a clogged injector cause the cobalt do not have gas filters that you can change and gas these days have some stuff in it that clog the injectors. I ran my gas tank empty got some fuel injector cleaner put it in filled up half way about a quarter of a tank later no more misfire and i just made an appointment at my old shop to have them look at it so i am pretty sure that is why it is misfiring. every so many thousands of miles i would put fuel injector cleaner in it like how i say run it to empty put it in and fill it to half a tank its good for the fuel system it cleans it out

The cobalt's do not have fuel filters you have to just clean them out with fuel injector cleaner, it might be the maf is dirty i have to check that but i also just posted about how i put the cleaner in and a quarter of a tank later its smooth as anything. as for the a/c i never put it on, it puts to much load on the engine takes away to much horsepower and makes it misfire i really just want to get ride of it but i haven't looked into that i might not be able to. tomorrow i am going to my old shop i used to work on it and hook up the scanner and check it out look it over completely with some of the guys there. they are really good with cars all them combined they can figure out anything.

 

The SS/SC has a fuel filter , i changed it when i had mine .

 

Its in the gas tank though right?

 

Nope right above the rear axle towards the passenger side.