Thread: GP Shaking Badly, raspy/loud exhaust. Need help!

Hey guys, sorry for making another topic so soon, but my GP is running horribly and I'm hoping someone might be able to tell me whats wrong so I could get it fixed. I'd take it to a shop tomorrow morning, but most of the shops around here charge outrageous prices if you don't know exactly what wrong with your car. I've had bad experiences and I'm hoping to get one step ahead..

My cat went bad a little while ago and I've been looking into getting new headers or a cat-less downpipe. I don't have the equipment to change headers though.

ANYWAY, I pulled up to a stoplight on my way home from work (Tuesday night) and when I came to a stop my car started shaking really bad. The lights started dimming and the engine felt like it was going to stall. The exhaust got louder and really really raspy sounding. The car would even act like it wanted to accelerate on it's own.

Let me specify more about the actual shaking. It's not an issue with the wheels/alignment. The engine/exhaust itself is moving a lot more than it should be while IDLE. If I look underneath the car or at the tailpipes, the pipes are moving/shaking a LOT more than they ever should be, and it's quite loud.

I really don't know what the problem would be, I'm not really advanced with cars I just know some of the basics. Also, I replaced Vacuum Tree/Intake Manifold Vacuum (Small plastic piece with 2 hoses, near throttle body) Wednesday during the day when I noticed one of the plastic pieces was broken off. I also changed my plugs and wires Wednesday.





I know that's a lot of reading, but I hope someone can help me with this issue. I would really like to get it to the shop asap or possibly have a friend help me fix it if it's not a HUGE problem. Thank you!

Do you still have a bad cat on the car?
If yes..then likely it's getting worse and or blew out.

Yes it's still there, I jacked the car up last night to look for any serious problems and I didn't see any holes or anything on the cat (but it does still need replaced.)

Do you think removing/replacing that would fix this problem?

I'd think that fixing a known issue, might help.

Well of course, I'm not against fixing the cat, I just wasn't sure if there might be other reasons it would be doing this.

I guess my next question is would installing a new cat be fairly easy by myself? I heard zzp has them but I was hoping for a bolt-on, so I could save some time.

The equivalent of what your car is going through right now..would be someone putting a supersized cork up your butt and making it so you can't pee. Then...someone keeps feeding you. You'd be shaking and acting funny too.

Likely your entire problem is a plugged cat and hopefully....not a negectful owner.

Well I knew my cat was starting to go bad, but I planned on just replacing it with a cat-less downpipe. Unfortunately I've only got one friend that can help me and he has been very very busy lately. I don't know any other mechanics or shop owners/workers. I just would rather change the cat myself if it's not too difficult, instead of paying a few hundred dollars.

I love my pontiacs and I hate seeing them like this .

What would you suggest for a replacement bolt on cat?

Thank you for the replies!

Hm?

Ah so they are bolt-on if you get the downpipe with it? Sorry for the stupid questions, I'm new to exhaust work.

Gotcha. Hmm I thought 04+ didn't have the u-bend?

Originally Posted by VejGTP

Gotcha. Hmm I thought 04+ didn't have the u-bend?

Correct.

W-Body Store prices are usually volleying back and forth with ZZP. Might be cheaper for the same thing.

Took it to the shop and they said piston 6 is failing. Not sure the exact cause, they are going to look at it further tomorrow. Valve or Head Gasket probably. Either way I'll still get a new cat after that repair is finished.

Sucks!