# Is 'cut and weld' a good option for replacing OEM catalytic converter?



## The_Dark_Knight (Nov 1, 2009)

I have a 2002 Jetta GLS wagon (AVH engine) with 74K miles on it. I have been periodically getting the P0420 engine code which potentially leads to the catalytic converter. The Federal Emissions Warranty is 8 years/80K miles so my car was too old. I called the dealer to confirm that it was still not effective under 80K miles and low and behold they tell me there was a WARRANTY EXTENSION on my car to 10 year/100K miles. YEAH!! Oh, but wait....the car was purchased in July 2002 so I missed this warranty by ONE MONTH!!! :banghead: 

I tried TWICE to get VW to still cover it but they refused.  I had the dealership confirm that it was indeed a bad cat. They charged me $95 for that but I felt it was worth it because VW would not even attempt to cover under warranty without a dealership confirmation of problem. The stealership wants $1600 to replace the cat (parts and labor). HA HA HA HA....what is in those cats? GOLD?? 

Anyway, I am thinking about replacing the OEM with a Universal Magnaflow ($67). I can't do it myself however, because I don't have a lift for the car and not much experience with welding. I know some shops that will accept customer provided parts and just charge labor. However, in some of my previous experiences, these shops tend to want to install DIRECT FIT parts rather than doing the old cut and weld act. 

So my question is if anyone has had any problems installing a universal cat in this manner on these particular cars? Some parts websites don't even offer anything other than direct fit which seems like a bad sign in my opinion. 

Also, I noticed from another post that I probably should get an O2 sensor spacer with this Magnaflow cat so that I don't get a CEL for the sensor. Is that really necessary?


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## Matt K. (Sep 2, 2012)

*We're screwed*

I have a 2001 Jetta GLS wagon AVH. MIL light came on. Same code, cat, I paid 67.00 for a independent shop to tell me that. VW said 14 mos. past Ext. warr, sooo sorry.:facepalm: 
I'm thinking we're screwed, I've talked to a fair amount of techs and these era cars are extremely sensitive. the later ones are recalibrated. 
My light has not come back on, about a week. I'm saving up and will address it when it stays on. Everyone I talked to say put the VW cat in, direct fit, or the light will stay on, and that's not good. 850.00 from VW


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## The_Dark_Knight (Nov 1, 2009)

I hear you man but there is no way I am putting down $1600 to the dealer for a new VW cat. The part itself is $1200 from them so that is still out of the question. I have read that some people have had success with the Magnaflow cat. I think what can happen is that these cats are more high flow performance so they screw with the O2 sensor that is in place AFTER the cat. That can be corrected with a spacer....or so I hear.....can anyone confirm??


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## The_Dark_Knight (Nov 1, 2009)

By the way Matt, I have had the P0420 code popping up occasionally (maybe once every few months) for over a year. I just clear it out with a scan tool from the parts store. I have not noticed any poor performance issues either, so you can certainly drive it for a while with a cat that is below par but not completely shot.


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## Matt K. (Sep 2, 2012)

*Cat trouble*

Thank God, I wasn't going to get worked up about it yet. What scan tool do you recommend? I think this is the beginning of it and can probably go awhile yet too. 
Side note, I paid too much for the car from the dealer, but it only had 70k and was really clean. Everything else I looked at in that price range had over 120k and wasn't as clean. 2 sets of rims and tires too, winter and new summer Michelins. 
I have friends that can get the part from dealer for 850. So it won't hurt as much, still not fun. 
Bad enough on the third tank I found out it burns oil (which everyone said "that's within spec.). That really .... me off. But there are people worse off then me.


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## The_Dark_Knight (Nov 1, 2009)

Also, be mindful that if your state has an emission inspection, it may not pass with the engine code registering. I had one done on my car a while back and I am fairly certain that I had seen the cat code pop up a few times randomly before that. I thought the cat might be bad and it would not pass the emissions inspection but it passed just fine so that told me the cat was still working well enough even though the CPU is throwing off this code once in a while. 

I go to Advance Auto to borrow their standard OBDII scan tool but I think other parts stores may lend them out as well. You can usually just take care of it in the parking lot and then take it back into the store when you are done. Easy to use....just plug in under the dash and follow the menu prompts to read codes and then make sure you erase codes before disconnecting it so the CEL will go off on the car. 

Just curious...how much did you pay for the car from the dealership?


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## Mike K. (Jan 30, 2004)

I bought a catalyticconverters.com type (had bung at engine end and pipe section coming out opposite end), paid like $200 delivered to my door. Had Car-X cut-and-bolt/weld this on for another $80. This was 45k miles ago, still going strong.


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## The_Dark_Knight (Nov 1, 2009)

Thanks for the feedback Mike. I assume you got no trouble codes after the install? Did you have to modify the O2 sensors at all?


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## Anony00GT (Mar 6, 2002)

The_Dark_Knight said:


> HA HA HA HA....what is in those cats? GOLD??


 Actually, yes. And Platinum. And Palladium. And a few other precious metals. 



The_Dark_Knight said:


> Anyway, I am thinking about replacing the OEM with a Universal Magnaflow ($67).


 There's a reason the VW cat is like $1200 and the Magnaflow is $67 (see above). You get what you pay for. A $67 ceramic cat will likely bring that CEL right back. 



The_Dark_Knight said:


> So my question is if anyone has had any problems installing a universal cat in this manner on these particular cars? Some parts websites don't even offer anything other than direct fit which seems like a bad sign in my opinion.


 See above. Get OE or get hosed. 



The_Dark_Knight said:


> Also, I noticed from another post that I probably should get an O2 sensor spacer with this Magnaflow cat so that I don't get a CEL for the sensor. Is that really necessary?


 Don't do it. Contrary to popular belief, the rear O2 sensor is actually used for fuel control. Primary fuel control in many instances. Taking it out of the exhaust stream will mess up fuel trims. 


Oh, and let me add this little bit: Figure out why the cat went bad. A failed cat is usually a symptom of an underlying problem. Also, I've seen catalytic converter fault codes caused by things other than a failed cat, and I've seen plenty of misdiagnosis, yes even from dealerships. If you can find someone in your area with VCDS there are some things you can check yourself to confirm before spending big bucks on a cat.


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## The_Dark_Knight (Nov 1, 2009)

I am fairly certain the cat is bad. I had some misfiring problems a while back due to the typical hairline cracks found on the ignition coil pack. The damage may have been done there or it could have been partially attributed to a couple service shops badly overfilling the oil on two different occasions. Having the dealership confirm is enough evidence for me. 

I am not having any noticeable performance issues and the car did pass the last state emissions test so I do believe I can keep using this one for a while. 

I appreciate the comments Anony00GT but can you tell me if you are basing them on your own personal experiences trying aftermarket cats or is your info from other sources?


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## bobinkski (Oct 8, 2009)

I have the P0420 for several months now, and what I have read about it there is no cure. Me spending $1200 on a VW cat. no way. Magnaflow and spacer, there are some people that have done that and it works. Looking back with my 02 Jetta AZG 2.0, I did have misfires, possible cause for the cat to go bad. I have possible fixed the misfire problem with a new ground wire from the coil pack to a new ground, and also filling in the cracks on the coil pack it self. I jacked up the car to look at the cat. it is brown like rust as the muffler is, I tried shaking/ hitting it to hear any gravel sounds and there was none. What I see alot of people are looking for is what worked for your car and what did not work. Now! let me throw this idea out to guys. What about running lacqure thinner through the system? I did alot of research on this idea and the only ansewers I have found is that "bad idea"no good for the engine" and so on. I like to hear from someone that has done this or has added a cleaner into the gas tank and what did it do? I have the state emission coming in March so I have afew months yet.


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## Anony00GT (Mar 6, 2002)

The_Dark_Knight said:


> Having the dealership confirm is enough evidence for me.


 Don't be so sure, you're out of warranty. EXAMPLE: I had a 1.8T Passat a few months back, customer came in with a $2800 estimate from a local VW dealer to fix his laundry list of codes (cat code, lean code, misfires, etc), they just wanted to replace a part for every code. After they peeled him off the floor, he came to me for a second opinion. Two small vacuum lines later, I had him back on the road with no codes and all monitors set ready. 




The_Dark_Knight said:


> I appreciate the comments Anony00GT but can you tell me if you are basing them on your own personal experiences trying aftermarket cats or is your info from other sources?


 Personal experience. VAG and Honda/Acura will very often throw CAT codes with cheap aftermarket cats.


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## Matt K. (Sep 2, 2012)

*cut N weld contd. How much I paid*

It was a bigger independent dealer in Madison not VW dealer. 7500.00 
It is a clean car, new Michelins, snow rims and tires, 70K, new side lights and headlights, clean underside. I wanted the lowest mileage car I could find, I wasn't even looking for VW. 
In this area 7500.00 was going to get me 140K car with more needs then I care for. 
Still too much, eager buyer, amazing 37 yr. old and still not perfect and all knowing .


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## Prof315 (Jan 5, 2009)

Anony00GT said:


> Don't do it. Contrary to popular belief, the rear O2 sensor is actually used for fuel control. Primary fuel control in many instances. Taking it out of the exhaust stream will mess up fuel trims.


 Hate to tell you this but until 2004 the rear O2 is used ONLY to monitor catalyst efficiency. Starting in 2004 OEMs began to use post cat O2 sensors for trimming fuel but total trim is less than 1% and it done specifically to maintain cat efficiency. 

That said removing the rear O2 will cause issues but not because it is being used for fuel trimming.


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## bobinkski (Oct 8, 2009)

Nobody can reply regarding cleaning the cat. I have read articles about cleaning agents along with lacqure thinner. Sounds to good to be true! may work if only had misfires? and all it needs is to be cleaned out.


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## Matt K. (Sep 2, 2012)

*cat trouble*

What about Sea Foam additive in the fuel or crankcase?


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## The_Dark_Knight (Nov 1, 2009)

Prof315 said:


> Hate to tell you this but until 2004 the rear O2 is used ONLY to monitor catalyst efficiency. Starting in 2004 OEMs began to use post cat O2 sensors for trimming fuel but total trim is less than 1% and it done specifically to maintain cat efficiency.


PIVOTAL info since my car is 2002. Maybe the Universal cat and O2 sensor spacer will work after all...thanks for the input!!



bobinkski said:


> Nobody can reply regarding cleaning the cat. I have read articles about cleaning agents along with lacqure thinner. Sounds to good to be true! may work if only had misfires? and all it needs is to be cleaned out.


I have never even heard of trying to clean the cat. I would suggest starting a new thread with that subject so that those who may know can easily see the question.


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## Cee-dub (Feb 20, 2007)

After my OE cat went 'can of marbles,' and after a similar dealer quote, I went with a Magnaflow high-flow cat. I've had a persistent P0420 since installing it (with 2.25" Remus exhaust), so have bought a 42dd spacer for the rear O2 sensor. I've got it on hand but haven't gotten around to installing it yet; will post back with my experience...

(2002 AZG.)


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## bobinkski (Oct 8, 2009)

Yeah, I should start a new post regarding cleaning the cat. Sorry for hijacking the thread if I did. Cee-dub, I have also a AZG '02. did you have your magna flow cut and welded in, or a direct fit? And what part number. The muffler shop by me wants $180 to cut and weld for a new cat.


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## The_Dark_Knight (Nov 1, 2009)

Cee-dub said:


> I've got it on hand but haven't gotten around to installing it yet; will post back with my experience...


Please do post your results. That info is vital. Thanks



bobinkski said:


> Yeah, I should start a new post regarding cleaning the cat. Sorry for hijacking the thread if I did.


No problem. I just figured that nobody was really able to see your question buried within this thread. You would probably have a much better chance with a new thread containing the question in the title.


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## Cee-dub (Feb 20, 2007)

bobinkski said:


> Cee-dub, I have also a AZG '02. did you have your magna flow cut and welded in, or a direct fit? And what part number. The muffler shop by me wants $180 to cut and weld for a new cat.


Direct fit, Magnaflow p/n 23710.

OP - Will try to report back in a week or so.


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## Cee-dub (Feb 20, 2007)

The_Dark_Knight said:


> Please do post your results. That info is vital. Thanks


Rear O2 sensor spacer is installed. Cleared the P0420 code. (That's all I need to do, right? Don't need to disconnect battery to reset learned values, do I? I don't have Vag-Com, just cheap OBD-II reader.)

I drove around for about 20 km with no recurrence (dare I say) yet? So strange not seeing orange on the dash... The beer store closed at 10:00 and I got there at 9:59.  So far fate is on my side!


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## ShelbyVNT (Nov 18, 2011)

The_Dark_Knight said:


> wants $1600 to replace the cat (parts and labor). HA HA HA HA....what is in those cats? GOLD??


 Nope not gold. Platinum actually, which is why a Catalytic core is worth 100 bucks.


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## The_Dark_Knight (Nov 1, 2009)

Cee-dub said:


> Rear O2 sensor spacer is installed. Cleared the P0420 code. (That's all I need to do, right? Don't need to disconnect battery to reset learned values, do I? I don't have Vag-Com, just cheap OBD-II reader.)
> 
> 
> > Yes, using your OBD-II code reader to clear out the code is all you need to do. I have a cheap one myself and do it frequently for the P0420 code.
> ...


 Sounds great so far. Thanks for posting your results. Check back in a month or so and let us know if the positive results are long term. I have gone maybe a month sometimes on my car after clearing the code before it would come back. Good luck!


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## Cee-dub (Feb 20, 2007)

The_Dark_Knight said:


> Sounds great so far. Thanks for posting your results. Check back in a month or so and let us know if the positive results are long term. I have gone maybe a month sometimes on my car after clearing the code before it would come back. Good luck!


Well, today my CEL returned, and I cursed! But, it turned out to just be a run-of-the-mill vacuum leak! Never have I been so excited to have a vacuum leak...

Five weeks later, still P0420-free.


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## The_Dark_Knight (Nov 1, 2009)

That's great!!

I keep getting the code pop up after I erase it with my reader but so far I have not noticed any performance issues. Even still, I think it is time to finally get that fixed. I found a guy that installs them for a good price and he uses 'AP' brand cat converters. He says those have been sucessful for him in holding off the dreaded P0420 code WITHOUT installing a J spacer. I think I am going to give that a shot.


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