Small background on my car.

-2006 SS/SC 24,xxx miles
-Megan cat-back. Been on the car for roughly 1,500 miles.
-WOT box. 2-step has only been engaged twice during the 1,500 miles.
-Rest of mods are in garage.

So, I after about 1,500 miles on the exhaust, it seems the resonator has possibly gone out on me. I get a TERRIBLE rattling when letting off RPMS above 2.5k (when they drop i hear the rattle) And my exhaust is blowing out Metallic, chalky stuff. I understand it blows some crap out when first installed, but not this much, this many miles later.

Well, I take the car out for a drive. WOT through first, notice a -tiny- stumble at 5.5k RPM. I make it to second, where it stumbles like mad, and the CEL will start to flash. It wont stay on, just flash. After it's done stumbling, it's SLOWLY crawl through the RPM's, and in third gear it WILL NOT go past 5k RPM. It just hangs there.

Mind you, I have the 2-step disengaged (turned completely off) unless I'm running the car at the track. So, it does not, in anyway, turn itself on at this time. The LED is in clear site and would let me know.

It seems to me like the engine is being chocked. I checked my CAI, it's there fine... checked all the solder to the wires on my WOT box, still fine. I've crawled under the car and can CLEARLY hear a rattle from the resonator.... I don't have the tools at this time to take it off and inspect it though.

I've contacted NGAmotorsports about this issue to warrant the exhaust... they've been a HUGE pain in my ass. First telling me to contact megan, when it CLEARLY states on the site to contact your distributor for warranty information.... so it's not like I can easily get a new resonator there to see if that's the issue.

Anyone have any idea what's going on???

 

could be a clogged cat

 

only reason i don't think that is because when i'm under the car listening for the rattle, it comes from the direct middle of the resonator on the megan exhaust.

that, and i never touched the cat... and my car only has 24k miles and i'd hope to god it wouldn't be clogged yet

 

send it in to megan they warranty it for like 12 mo.

 

theres been people with clogged cats at like 8k miles, it happens. gm rich tunes....

i have the megan and it only rattles because i hit the freaking heat shield fixing it so it would stop sliding over and the heat shield rattles.

 

I bet you blew part of your cat out and that is what you hear rattling around in your resonator.

Also, did you make sure to bend and mold your heat shield so it would not hit the exhaust when you did your install?

 

Read the end of the post. I'm dealing with that BS through NGAmotorsports.... their customer support is extremely lacking....

I can still hope it doesn't, because now that's out of warranty since I added the cat-back.

Anything that would make me blow out the cat? I'd say 2-step... but I've VERY rarely ever engaged it.

Yeap, nothing is rubbing or hitting anything on the underside of the car. When i first heard the rattle, that's what I assumed it was. It's 100% clear all the way around, and the rattle is directly from the resonator...

Also, if the cat was blown, wouldn't a CEL stay on?

 

well the exhuat wouldnt really void the cats warranty, remember they have to prove the exhaust made the cat clog....

 

if theres metallic stuff comin out.. it definately sounds like a clogged cat to me... however a flashing CEL is probably becasue the engine is misfiring once it hits 5k rpms and is preventing you from going any higher then that.

 

i DO know tomorrow I'll be taking the resonator off the car to take a look....

If there's nothing inside of it, what should be next plan of action be?

 

see if u can get the code read.. if not then check the spark plus and coil packs.. those are 2 things that often cause that... Someone correct me if im wrong, but i think an engine misfire can cuse damage to the cat?

 

Yes an engine misfire can cause damage to the cat since you are dumping large amounts of raw fuel into the cat, which is what kills it.

 

i've known a car to just FLASH a CEL... so is there going to be something to even pull? I figured if something was wrong the cel would stay on.... but, new to cobalts. Only had this car since April.

it also doesn't misfire often. Only if i go WOT. and i heard the rattling before the mis-fire happened...

just trying to spew out as much info as possible so i can hopefully get this crap fixed tomorrow.

 

2 step+ gm rich rich tune = clogged cat

you probably killed the cat while using the 2 step. A "broken" catback would NEVER cause a mis fire, cell or any of the problems that you have. Also, the catback won't void the cats warranty, but the wot box sure will.

 

Well then. If that's the case, WOT box comes off to take the car into the dealer for warranty work.

This would also go along with the cat being clogged, but I noticed my exhaust has mellowed down a lot actually.... It's not nearly as loud or drones much on the highway anymore.

Can't i just knock all the guts out of the cat and call it a day? Or take it into an exhaust shop and have them weld in a pipe in place?

I figure why get another cat if my 2-step will kill it again....

 

no.. doesnt matter what car you have a flashing CEL is never just alright.. you need to get it checked out before more damage is done

 

I'll just not going WOT until I figure it out, since that's when I notice all these problems.

And I'm used to, if there's a problem with the car, the CEL stays on, i get it scanned, figure out problems. I'm questioning if there's anything to even scan if the CELs not on.

 

ya flashing cel is bad. if its solid and there are no driveability issues then you can go a little bit but still need to get it looked at for whats causing the cel. and the cel's are stored in the car's history until manually cleared.

 

anyway to check codes out without a reader?

on my dodge all i had to do was turn the key 3 times and it'd display it in the cluster. Does chevy do anything like that?

 

Actually a solid cell isn't always bad. I throw P0420 codes all day long. Of course, the ECM doesn't like aftermarket cats. Oh well.

 

that, and if you're scared of getting a CEL from time to time, you shouldn't mod a car

i guess i'm just used to them from screwing with stuff over the years.

 

that was with obd1. and no you can't check the codes without a scanner that i am aware of.

 

Well then... Damn it all.

List of crap to do tomorrow then... Take off resonator, clean. tap cat a few times, see if anything drops out of down pipe. Take for ride, she what car is doing. If still acting up, take off WOT box, sell, take car to dealer, act stupid.

Sound good?

 

lol sounds good to me lol.

 

well it really sounds like your cat. of course gm will warranty it and actually the newer cats they installed on mine is far better then what i see installed on stock. maybe they are better, maybe they are the same. but mine was clogged at 16k and caused missfire. dampened tone to exhuast and huge rattling. also you should also notice your boost guage going higher then normal under high rev becuase of the back pressure. mine caused damage to the timing chain tensioner....actually it blow apart. so be very careful. dont stress her out and everything will be ok. if you have to get rid of the cat for some odd reason. you have to do a cat delete and null a o2 sensor. this may void your warranty.

good luck