Replacing catalytic converter

[95SevilleSLS]

I want to replace the catalytic conerter on my 02 because I believe that is where all my problems (not so good gas mileage, not as much power as my 97 had, shake/shimmy at idle) are stemming from and knowing that in 02 GM had their share of faulty converters. My dilema is that I'm not sure which converter to go with. Both are AC Delco but for $75 I can get a universal one and for $300 I can get a direct fit. The only bad thing about the universal one is that it will make it a little louder. I don't really want my 02 any louder, but how much louder could a cat make it? Has anyone replaced a cat with a universal one? Which way should I go here?

Thanks for the help in advance!

[koushka]

I am about to replace my cat as well on Monday. My exhaust guy is just grabbing a direct fit, but I am not sure from where, I will ask him. After digging thru the forums, Jim had a recent replacement and I think it seemed to me that the universal requires welding, brackets, and O2 sensor mounting. While the direct fit has that stuff on it. If you can find someone to get the brackets and things on the universal, I would go with that just to be cost effective. I doubt you will really notice any change in noise but I can let you know when I get mine done if you would like. Good luck

peter

[Cadillac Jim]

Any good muffler shop that welds stainless steel with rustless welds can deal with a universal cat easily. The universal won't make your car any louder because the cat had very little to do with silencing. The most important differences are that if you want CA OBD II certification, it's very hard to find a universal because it's hard to certify to CA standards without the whole thing there, so if you want CA OBD II certification you probably should just look at direct fit.

Cadillac isn't viewed as a high performance car by the masses, and that includes nearly all mechanics, so you need to be sure that the cat you buy will flow as freely as the OEM, which is really good. That's one of the biggest reasons that I went with a high-flow.

When you use a universal, the flange is cut off the old cat and re-used on the universal. On VIN 9 engines that come as part of the Touring packages (291/295/300/320 hp), you need to be sure that the muffler shop puts the cat as close as possible to the flange or that last torque peak will move down a few RPM. Just tell them to mimic the configuration of the stock cat.

I didn't have a problem with the oxygen sensor. I think mine came with two oxygen sensor pads, but the installer may have used the ones on my old cat.

My cat is a MagnaFlow 94109. It's got 49-state OBD II certification so you can be sure that it works, and you won't have trouble come inspection time.

[95SevilleSLS]

Did you buy yours directly from magnaflow? Now I'm really confused one what to do! I know I don't care about noise anymore, but I'm not sure about the O2 sensor thing. I'm a little scared of the muffler shop now because he isn't with it all the time if you know what I mean. You'll tell him one thing and he'll forget it 2 minutes later. I'll have to take a look underneath to see if there will be any fusing with the O2 sensors.

I also don't care about CA certification. I live in North Dakota and we don't even have emission checks so I'd be fine with even leaving it off! I'll do some checking around and see what I find.

[BodybyFisher]

I bought a universal cat for my 91 Seville from NAPA and had Midas weld the rear of it for $30. It worked fine.

[95SevilleSLS]

I bought a universal cat for my 91 Seville from NAPA and had Midas weld the rear of it for $30. It worked fine.

Did it sound any different?

[JimD]

....I also don't care about CA certification. I live in North Dakota and we don't even have emission checks so I'd be fine with even leaving it off! I'll do some checking around and see what I find.

If you can convince a dealer that the converter has failed, the Federal mandated emissions system warranty might pay the freight. The attached file is a simple converter test with a vacuum guage.

CA or no CA, you do care. Federal law prohibits tampering with emissions systems and provides potential for a heavy fine. Plus you could have difficulty selling the car to a knowledgeable buyer.

Removing or disabling O2 sensors will mess up the ability of the PCM to run the engine in closed loop resulting in codes, Service Engine Soon lamps, fuel economy/performance hit, and more.

[BodybyFisher]

I bought a universal cat for my 91 Seville from NAPA and had Midas weld the rear of it for $30. It worked fine.

Did it sound any different?

Not at all, the 4.9 had a very throaty sound, it didn't change at all, I think the mufflers have more of an impact on that, Mike

As Jim said, 02 was a bad year for GM CATS..... they will replace it for free

[Logan]

Uh....if your under 80K it may be under FED warranty. OBDII FED covers the Cat and PCM for 8 years and 80 k miles..

[95SevilleSLS]

Yeah, I knew about the warranty and I wish I would have bought the car a little sooner. I bought it with 80,500 miles on it an dit now has 83,500. I don't think they'll replace it for me.

JimD, I know that it's illegal to tamper with that, I wasn't suggesting that I was GOING to take the cat off, I was just simply stating that ND doesn't check anything. I don't have any codes or lights, and I knew about the 02's having problems with cats that's why I assumed it was the cat. Is there just a general vacuum gauge that would work for testing this or is there a special one that will hook to the manifold. Where would I hook it to the manifold?

[JimD]

Any vacuum guage will do what you need. Simply plug the guage into any vacuum line you can locate in the area of the throttle body.

[Cadillac Jim]

Nobody is going to prosecute you for a good-faith repair that produces an emissions-legal car. Uh, unless you have a local prosecutor that is running for office in Oregon. If you have any doubts, have your mechanic run an emissions test after installation.

I bought my muffler online for about $67. I think I bought it from The Performance Peddler, but my cat is a standard one that is available lots of places. I found TPP's posting of this cat with a dogpile search on the part number, which was recommended in a Caddyinfo post. Installation was under $100 including all welding, and it took about a half day because my mechanic supervises his whole shop. Also, he scheduled the job for a slow day so he could take his time with it. I have seen my car on a rack several times since and see a new oxygen sensor on the outlet side of the cat. Since my cat is OBD II certified, I have all confidence that it will pass emissions testing anywhere, including CA. My car is a CA car but it has been garaged on the East coast since 2000 and I have no plans to move. If I ever need to register it in CA in the future, I will deal with any issues that arise at that time, and I don't expect that any will -- my car will be just another out-of-state car that needs a tailpipe test and I'm sure that it will pass easily.

Not many aftermarket cats are OBD II certified. I think that OBD II certification is worthwhile because it guarantees that, properly installed, you won't have problems in the future. Also you should be sure that the cat you buy is guaranteed to work with your car; if in doubt with the listing, call the vendor and/or manufacturer before you try to install it.

If you think that your cat might be clogged, you may be able to tell by unbolting the flange at the exhaust manifold collector and looking in with mirror and a flashlight at the other end. If you can't see through all the holes, it's partly clogged (like mine was). If you can't get a flashlight to the other end, you probably can see the clogging with both the light and mirror at the flange end.

[BodybyFisher]

Any vacuum guage will do what you need. Simply plug the guage into any vacuum line you can locate in the area of the throttle body.

While I know its suppose to work, I didnt have much luck using a vacuum gage to diagnose my the bad CAT in my 2002 Monte Carlo. The engine had no power at all. I did a laundry list of diagnosis and ended up taking it to the dealer. After seeing what I did, the dealer knew immediately it was the CAT.

I previously posted a CAT tester that screws into the O2 sensor port that measures back pressure also

[95SevilleSLS]

Any vacuum guage will do what you need. Simply plug the guage into any vacuum line you can locate in the area of the throttle body.

While I know its suppose to work, I didnt have much luck using a vacuum gage to diagnose my the bad CAT in my 2002 Monte Carlo. The engine had no power at all. I did a laundry list of diagnosis and ended up taking it to the dealer. After seeing what I did, the dealer knew immediately it was the CAT.

I previously posted a CAT tester that screws into the O2 sensor port that measures back pressure also

I got that post of the tester, but the tester is half the cost of a new cat. I just figured it would be a lot cheaper to just replace it. Otherwise I'll spend $40 on the tester and find out it's the cat and spend another $75 or I could just get the cat. But if it is good, then I will have spent a little more on the cat.

I hope that made sense. It sounded kind of funny to me.

[koushka]

I had it done yesterday and it sounds no different then before. They used a universal fit which is basically the cat itself and welded it in there.

peter

[95SevilleSLS]

Any difference and performance/fuel economy?

[koushka]

As far as mileage goes, I am on vacation and am not running the normal routine so I am not sure, I do know its not any less but its not any better as of yet. Performance wise I see no change.

peter