Car all of a sudden sounds like a race car

[chopperman]

So Im driving down the belt parkway, my motor is misfiring so im only at 60 and Im trying to stay on the throttle as much as I can because if i slow down it will take forever to get to speed again. ANYWAY the misfiring went away and I was now at around 70mph and was cruising around happily. All of a sudden I hear a really deep sound. I decided to get to my desination instead of pulling over. When I get there my car sounds like I fucking put a exhaust system on it. Its nice and deep. I love the sound but I what to know what is wrong with it. I must say that my check engine light was on and when I checked it 2 weeks ago it said that my precat was messed up. I had an appoitment with the dealership to replace it because I heard it was under warranty when the car is under 80k miles but I wasnt able to go. Now Im gonna make another one. Can anyone tell me what is wrong or happened. It just all of a sudden started making this deep noise. I still have exhaust coming the tail pipe. Can it be that it has a hole in it? Thanks

[Kansei]

That's a really, really bad misfire. Happened to me when both of my aftermarket plug wires went bad.

Was your CEL ever flashing?

[JOMO]

also could be that your gasket in the precat is bad, causing a exhaust leak.

[chopperman]

Yes my cel was flashing because it was also misfired a little last night. Is that gasket covered under warranty

[JOMO]

Yes my cel was flashing because it was also misfired a little last night. Is that gasket covered under warranty

Should be, but it does sound like a misfire though. Check your plugs if you can.

[Spitfire70]

Sounds like an exhaust leak to me.

[TheMAN]

you killed the cat because you drove around with the flashing "CEL" when it was telling you NOT to drive it

now that you broke other shit in your car due to your neglegence, you may have to pay for those broken parts

[Kansei]

Don't assume it's negligence Edwin. I had to drive my car for a few miles with the CEL flashing (it only flashed under heavy throttle though, so I avoided as much as possible) because it was an emergency and I HAD to get where I was going. Luckily I don't have a pre-cat and it didn't wreck my high flow cat. But yeah, I also am completely ok with paying for broken parts.. nothing on this car has ever broken that I didn't cause.

I'm fairly certain the owner's manual does say to definitely never drive the car with a flashing CEL... people should sit down and read through the manual the first day they get the car, hell I even did that the first day with my G5 rental car :P

[chopperman]

car has brand new stock plugs that I put in about 2 months ago.

[Kansei]

car has brand new stock plugs that I put in about 2 months ago.

what about the plug wires? both of my (admittedly aftermarket crap... sparkco (rant)) plug wires were kinda bad and then got wet and caused all sorts of misfiring.

[chopperman]

no i didnt change the wires, Ill try that. But is the noise from my cat? Cuz i sounds like it is coming from the middle of the car and not the rear. I am assuming it is the gasket.

[Kansei]

Well if the noise is happening when the CEL is flashing, that's the sound of catastrophic misfiring and yes it is a wild sounding thing. How many miles are on your stock wires?

[chopperman]

I dont think they were ever changed car has 78k. I dont think it is misfiring, I still have all my power and it doesnt have slow acceleration or any symtoms of misifiring. When my motor was misifing the cel stays flashing for a couple of days until it will stop. So I doubt it could ne catastrofic misfiring.

[Kansei]

All your power still? well that's interesting! I'm starting to think maybe your cat is plugged from when you drove it while misfiring.

[P-Funk!]

^x2. And then a seam opened up relieving the back pressure. Inspect the exhaust system carefully.