• The site migration is complete! Hopefully everything transferred properly from the multiple decades old software we were using before. If you notice any issues please let me know, thanks! Also, I'm still working on things like chatbox, etc so hopefully those will be working in the next week or two.

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

VejGTP

VejGTP

New member
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!
 


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?
 
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. :th_winking:
 


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!
 
ZZP aluminized downpipe with catalytic convertor. Mine was about $200...can't remember if I got the gasket option.
I think there's only 5 bolts and a rear O2 sensor. You may need some deep-well metric sockets to remove the 3 nuts from the manifold as they are studs.
It took me about 20 minutes and there was a beer or two in there somewhere.
 
Ah so they are bolt-on if you get the downpipe with it? Sorry for the stupid questions, I'm new to exhaust work.
 
Yea, ZZP refers to it as "bolt in with cat". It comes as one piece and they've also welded the O2 bung in place.
The other thing they do is delete the U-shaped section right before the cat-back. This frees up some flow.
 


VejGTP said:
Gotcha. Hmm I thought 04+ didn't have the u-bend?
Click to expand...

Maybe so. Mine are 2000GT and 2002GTP and they both had the U section.

You know if you're up to the challenge you can weld a Magnaflow in there (since you don't have a u-bend). It's fairly easy.
I did one of catalytic convertors on my Mirage (it has 2)...cut old cat out with a Sawsall and loosened the bolts. There was enough play in the exhaust to wiggle the new cat in place and tightened the bolts back up. After three spot welds I dropped the entire pipe and welded it the rest of the way on the bench. My cheap flux-core welder worked real well.
 
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!
 
You must log in or register to reply here.
Back
Top