Here's the scoop, bought my 02' SS three weeks ago. It idled decent, slight roughness to it. Orignal owner didn't do any preventative maintenance other than change the oil/filter every 3,000 miles with Mobil 1 since he bought it new off the lot in 02'. So I changed the fuel filter a week ago, and it seems to help the idle alittle bit. This past Friday after reading all the good reviews on SeaFoam I tried it, shortly after letting it sit for a couple hours and firing it up to let the crap burn off it throws a P0300 code (Random/Multiple Cylinder Misfire Detected). After most of the heavy smoke was gone, shut it down, erased the code, and take it for a 2 hour/200+ mile drive. Sunday I fired it up, idle roughness was still there but it did idle lower (800rpms compared to 900), installed a set of MSD 8.5 LS1 wires and NGK TR55 (gapped @ 0.55) since I figured from the research on here most stock plugs don't last that long in our LS1's. Didn't get a chance to drive it yesterday, and on my way to work today I noticed it was idling even rougher than before. Now 2 days before doing the seafoam (last wednesday) on my way to work the infamous P0420 code popped up and I erased the code at home with my scanner. Here's were it gets weird (at least to me being a new LS1 owner), during my 2 hour drive the ses never came on at all then all of a sudden P0420 code pops up again on my way home from work today.

Could having a soon to be clogged cat be causing this rough idling? Also even though I posted it in the Western forum has anyone had good luck with a local Southern California dealership about replacing the cat under the GM federal 8 year/80,000 mile warranty with a slightly modified vehicle? Don't want the hassle, wasted money, wasted time if a dealer is going to tell me "Sorry you have aftermarket headers (BBK shorties) and intake (K&N FIPK)that caused the cat to go bad".

Sorry for the long story, wanted to be specific as possible on what happened. Any help is greatly appreciated, thanks.

 

Burden of proof is on the dealer. They have to prove your shorties and FIPK (which are both DOT legal btw) caused the cat to go bad. I had my driver side cat go bad on me after 10,000 miles with the stock manifolds.

 

eidt: wrong post

 

I think it's deffinatly a cat. Those where the same exact syptoms my pick up had. It was actually throwing a P0300 before the P0420. I spent months trying to track down the problem and then the cat finally started to rattle at idle and I got a P0420. GM should replace that no questions asked. My truck ran a 100% better after.

 

and thats why I don't have cats

 

Wanted to updated everyone on the progress of the cat ordeal. Took the SS in on Thursday morning to a family recommended dealership. The service guy was more than willing to help me out in any way possible. They are not only replacing the drivers side but also the passenger too, getting the pinion seal done as well since it started to seep before I bought it. The great thing about the GM extended warranty that the orginal owner bought is since the smog tech at the dealership called in sick friday (couldn't complete the cat replacements) I get a free rental vehicle until it's finished, which I wasn't aware of till the same service guy told me about. Guess it goes to show not all dealerships aren't ********, if anybody in the SoCal area wants the name & location of the dealer feel free to PM me. Thanks

 

Sounds great, hope they get everything straightend out for you.

 

Thanks GM, got my car back today. They did replace both cats under warranty, did the pinion seal & diff. cover gasket/gear old change, frontend alignment (had to pay $30 for that), and the temp gauge didn't act up (weird?) on them so nothing was done with that. It does run better, will have to drive it for a couple of days though to get a better feel cause the burning smell of new cats sucks. LOL I've got to hand it to the service guy that helped me, he may be an older guy but he'll help you out in any way without any hassle.