# Replacing a catalytic converter, MKIV Jetta GLS 2.0, AVH engine



## Julian Tempest (Aug 12, 2010)

Last request thread, I promise! 

So I replaced my coil pack, wires, and plugs because of misfires, but it seems I may have burned out my cat. I might like to try to replace mine with an OEM cat (or other cat that won't trip the CEL), but $900 is a lot of scratch. 

The closest thread I could find on this was here: 
http://www.hubgarage.com/mygarage/david/blogs/383 

But that's for a V6. It looks like a simple enough job to unbolt the bad pipe prior to the flex tube and bolt on a new one. Can someone point me to a good, cost-effective option for this? 

Thanks! 

Luke


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## builtvw (Sep 20, 2009)

yah but its not as easy as you think. i garentee that its cover in rust and youll have to snap bolts to get it off. just spray them with blaster and let it sit and pray/ make sure you get new bolts


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## builtvw (Sep 20, 2009)

and obviously gaskets


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## Julian Tempest (Aug 12, 2010)

The upside (which is really a downside) is that I replaced the entire exhaust pipe system about a year ago. Guy charged me $700 to replace the cat, the muffler, the O2 sensor, the flex tube, and all the piping in between, including the tailpipe. It's been a good cat for awhile now, and I've never gotten a check engine light on it until recently when my car started misfiring a lot (long story). 

Actually, I called him recently to find out how much he'd charge me to just replace the cat again and he said it'd be $185. That...sounds too good to be true, ya know? He'd said before that he'd put an OE cat in it, and the CEL cooperation seemed to confirm that, but at that price, I gotta wonder what corners he's cutting, hence I'm thinking of just doing it myself. That and he's 2 hours drive from where I live now. 

Anyway, so the upside is that since it was done a year ago, it shouldn't be too rusty, I would think. 

Good point on the gaskets; I hadn't thought of that.


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## Anony00GT (Mar 6, 2002)

$700 for all that work is REALLY cheap, unless you brought some of your own parts that weren't included in that price. Highly doubt that was an OE cat, probably a good aftermarket unit. 

He's probably going to replace the cat under warranty, that's why it's so cheap. No way you're going to do it for $185 even yourself.


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## Julian Tempest (Aug 12, 2010)

Yeah, I'd thought $700 was super cheap, too, especially since another mechanic had quoted me $800 just for the part. I'd figured at the time that if it worked, cool, but if the CEL popped on for it, then I'd hit him up about it. It never did, so I've since assumed it was either a great aftermarket, or the markup on dealer parts is ridiculous. 

I've since learned about ways to fool the system via the post-cat O2 sensor, and since he replaced that and it's now giving a CEL, I wonder if maybe he didn't cut a corner there. I figured rather than pay him $185 to put in another cat that may or may not be right, if I could find an OEM cat or exhaust assembly for something like $300-$500, then I'd do it myself with parts I know are good. 

I'm replacing the O2 sensor myself once my thermostat comes in (doing three things at once), so I'll see then if I toasted my cat or if it's a weak cat from the get-go. If it is bad and I can't find a cost-effective way to replace the cat myself, then I figure I'll mark my O2 sensor and drive up there to have him replace my cat for $185. The possibility of saving $900 is worth risking $185 and a day out of work.


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## Anony00GT (Mar 6, 2002)

Finding a used catalytic converter is not gonna happen (or shouldn't happen) for two reasons. 1) It's illegal to sell/install a used catalytic converter and 2) All used converters get recycled almost immediately anyway, they're worth a lot of money in scram for the precious metals inside them. 

Exactly what problem(s) are you having? What fault code(s) or symptom(s) are you trying to fix here?


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## Julian Tempest (Aug 12, 2010)

Good to know. I wasn't actually thinking of getting a used cat, but I was hoping that like many other parts, maybe I could get the cat from the manufacturer without having to pay dealer or shop markup. The O2 sensor, for instance, is $180 from my mechanic, but I got the Bosch one with wiring already done for $90 at Advance, and could've gotten the kit for $65 if I'd cared to just do the wiring myself. 

Anyway, I was getting p0420, but it hasn't popped up again since I replaced the plugs, wires, and coil. I'm still getting p0141 and p0036, so I'm replacing the O2 sensor and will see if that causes p0420 to pop back up. 

From what my mechanic told me, running with a misfire can burn out a cat in 5-10 minutes. The engine's passing gas into the cat, which the cat burns, overheating the cat and causing parts to melt and fuse. I've been driving the car with misfires in wet weather for a little over a year, but when the car started misfiring constantly, I drove it for about 5 days until I got the coil, which didn't fix the problem, so I took it to a mechanic, who replaced the plugs and wires, which did fix the problem. 

Upside is that now I don't misfire in wet weather either, and the coil I'd replaced was visibly cracked and corroded, so that wasn't a waste. I just wish I'd replaced the plugs and wires before going to the mechanic, since it cost me $315. I'd had those replaced first at what I thought was a reputable shop about a year ago when the wet weather misfiring had started. Turns out they put Chevy plugs and wires in my car, and the recent misfiring was caused by a burnt out plug and wire. I kept the parts so maybe I can hit that other shop up for a refund. 

Though I did learn a lot from the local mechanic. I can't believe I never knew that a blinking check engine light means "pull over NOW; continued driving will cause serious damage" (in this case, probably my cat). Yeah, dumb, but now I know. Few other lessons, like how to apply dielectric grease, all that about burning up the cat, what the O2 sensors do, and other stuff. Yeah, I got a lot to learn.


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## Anony00GT (Mar 6, 2002)

Call your local dealership and see how much they want to sell you a cat over the counter. OE is the way to go, or at least get an aftermarket that's certified for California emissions. There's a reason for the price difference. 

You did the right thing with the O2 sensor. The "universal" sensors where you splice the wires yourself are junk. On VAG cars, use only Bosch direct-fit oxygen sensors. Of course it was cheaper for you to get it at the parts store yourself. Your mechanic is getting it from a parts house and paying the same $90, selling it to you for $180, making a 50% profit margin. That's reasonable, most shops operate on ~60% margin. 

A blinking CEL means the ECU is detecting misfires that are potentially catalyst damaging, it doesn't mean pull over this second because the engine will go up in a big fireball. Driving with a blinking CEL does have its risks, and at the top of the list is catalyst damage. It usually takes a little more than 10 minutes though :laugh: 

Replace the O2 sensor and clear the codes. You may not even need a cat.


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## Julian Tempest (Aug 12, 2010)

So the blinking CEL is specific to cat-damage misfires? Guess that makes sense. He'd mentioned that's what it meant, but I got the idea that it was more general. 

But yeah, I'll check with the dealer on the cat, and once I replace the O2 sensor (this Friday, probably), I'll post back with whether or not the cat problem pops back up. 

Thanks!


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## Anony00GT (Mar 6, 2002)

Julian Tempest said:


> So the blinking CEL is specific to cat-damage misfires? Guess that makes sense. He'd mentioned that's what it meant, but I got the idea that it was more general.


 Yes. That's standard on any OBDII (1996+) vehicle. A blinking CEL specifically means catalyst-damaging misfires are currently occurring.


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## squabeggz (Feb 20, 2009)

Also make sure that the TSB for the coilpack ground wire has been done. I have the same MKIV GLS 2.0 AVH engine. I was dealing with misfires for a year plus. I replaced the plugs and wires with OE plugs and Karlyn/STI wires. My coil pack wasn't too bad, had some small hairline cracks which I covered with JB weld. Still had misfires. 

I then found out about the coilpack ground wire TSB and that still needed to be done on mine. After that was done, the misfires were practically gone. Occasionally popped back up though. At this point, I completely went over every grounding point in the engine bay cleaning and checking the wires and ground points. Cleaned up a bit of corrosion. Much better and no more misfire codes. 

I then started to get a bunch of very alarming codes dealing with the O2 sensors, Cat, CTS sensor and one that leads one to believe the ECU was fried  

After much research and troubleshooting, I found out that my CTS (coolant temp sensor) was bad...very very bad. It was a cheap chineese autozone replacement. I replaced that with an OEM green top. Suddenly all my codes were gone. CEL free now. Didn't have to replace any very expensive parts (ECU or cat or O2s). 

Sorry for rambling. Long story short. check your codes for seemingly unrelated issues, and check your grounds and most importantly...OEM SENSOR replacements. You may be pleasantly supprised that you probably dont need a new Catalytic converter. Here's hoping. Good Luck! 

Oh and one last thing. I was also getting flashing CEL only occcasionally...usually after I tried to fix something like a throttle body cleaning. I have 100k miles on my 2001 AVH with the original catylitic coverter, so it most definately should not melt within 10 minutes.


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## Julian Tempest (Aug 12, 2010)

Little new to the lingo here, and Google hasn't helped me given the five-minute rule. So...what's a TSB?


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## squabeggz (Feb 20, 2009)

Technical Service Bulletin 

Somewhere I have the .pdf of the actual TSB. I'll see if I can find it. 
Here are some links that deal with it as well. 
In this vortex thread is actually the TSB info with part numbers: 
http://forums.vwvortex.com/showthread.php?4913317-its-driving-me-nuts!!!! 

This video actually shows the procedure. Helps to see what is being done, so you can do a quick check to see if is has already been done to your car... 

Jump to about 6:46 to see the procedure. I still reccomend watching the whole video though. 
http://www.youtube.com/watch?v=FjGkFqdS52w 

You are basicly looking for a wire that has been spliced into the coil pack connector that runs to the grounding stud under the battery tray.


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## Julian Tempest (Aug 12, 2010)

Awesome! I'll check on this today after work. Thanks! 

So I did a bunch of work yesterday, including replacing the O2 sensor, then swung by Advance to clear my engine codes. The CEL hasn't popped back on yet, and my commute to work is about 30 minutes, so it seems that my cat is still good. Huzzah! 

It's definitely a Magnaflow, according to the stamp into the metal.


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## Anony00GT (Mar 6, 2002)

If you have VCDS you can run all the monitor tests and confirm the cat (and your O2 sensor repair) without moving the car at all. Then you'll quickly know for sure what the status is :thumbup:


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## Julian Tempest (Aug 12, 2010)

Yeah, I'm in the process of getting a VCDS now, along with a bunch of other parts from ECS Tuning. 

My CEL came on yesterday on the way back from work; p0420 and p2181 are back. p0420 I expected (and feared), but p2181 was the entire reason I replaced the thermostat. Maybe the CTS is bad? It's a green top. 

I think I'll just wait until my VCDS comes in before doing anything else.


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## Anony00GT (Mar 6, 2002)

Julian Tempest said:


> I think I'll just wait until my VCDS comes in before doing anything else.


 Good idea. Post back when you get a complete scan :thumbup:


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## nosborn94 (Feb 7, 2010)

Did you ever solve this issue?


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## Julian Tempest (Aug 12, 2010)

I got the VCDS, but got crazy busy after that January and still haven't gotten around to replacing the cat. Still have the same check engine light. 

And actually, it turns out I'm overdue for a timing belt change, so I need to find a shop that'll do that reasonably. Not something I can do myself, I don't think.


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## child_in_time (Aug 9, 2006)

I just replaced catalytic converter on my 05 Golf, BEV engine, for about $740 parts and labor, it was an aftermarket unit. The flex pipe on the cat was burned out and car was making all sorts of noises and would not pass inspections. 
I've had a letter from VWoA stating extended warranty on the catalytic converters to $120k miles or 10 years so I sent them the bill and they reimbursed the whole amount. 
Few days after that cel came with P0036 code for a oxygen sensor, I purchased one from local auto store for $95 and changed it myself. Probably old oxygen sensor did not like the new cat.


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