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Go Back   TDIClub Forums > TDI Model Specific Discussions Areas > VW MKIV-A4 TDIs (VE and PD)

VW MKIV-A4 TDIs (VE and PD) This is a general discussion about A4/MkIV Jetta (99.5-~2005), Golf(99.5-2006), and New Beetle(98-2006). Both VE and PD engines are covered here.

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Old October 11th, 2006, 09:07   #1
veget8
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Default Clogged Catalytic Converter?

I am experiencing problems with top end power output. According to a VAG-COM, my (brand new) MAF says that my actual flow is 450-550 (request is 800+) at 3000 rpm. I have pretty much eliminated the possibility of a problem with anything in the intake path.

My question is, has anyone ever experienced a clogged catalytic converter or other exhaust component? What was that like?

Another question- I shudder to think how much VW probably charges for the cat on these cars. Are there any lower cost options? Would any cat work ok, such as one made for a gasser?
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Old October 11th, 2006, 09:38   #2
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Quote:
Originally Posted by veget8
I am experiencing problems with top end power output. According to a VAG-COM, my (brand new) MAF says that my actual flow is 450-550 (request is 800+) at 3000 rpm. I have pretty much eliminated the possibility of a problem with anything in the intake path.

My question is, has anyone ever experienced a clogged catalytic converter or other exhaust component? What was that like?

Another question- I shudder to think how much VW probably charges for the cat on these cars. Are there any lower cost options? Would any cat work ok, such as one made for a gasser?
Symptoms of a clogged CAT:
1. Lack of or poor top end performance. Nopted by a limit of top speed. This is affected by the amount or degree of clogging. I've seen a TDI CAT clogged so badly that the top speed was 55/60 MPH.

2. Another symptom is excessive low /poor MPG on a 5 Sp I've seen MPG drop from 50 to a low of 38 MPG.

3. Excessive black smoke under attempted heavy acceleration

I also noticed that acceleration in 1st, 2nd & 3Rd gear was close to normal excepth when WOT in 3rd gear.
WOT in 3Rd resulted is a noteable sluggish feel. The car would accelerate but rather slowly.

About replacing your CAT...The CAT on a diesel is not the same as a "gasser" CAT. You'll need a diesel CAT.
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Old October 11th, 2006, 12:29   #3
veget8
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Thanks herm- that definitely describes what I'm seeing. I will look into a replacement diesel cat. I'm not particularly attached to having a cat, but it seems like I ought to have one in order to be legal. I see there is magnaflow cat. converter available for this car:

http://www.as-sl.com/car-sound/ficha...&ma=33&md=2229

Looks expensive and "oem like". Anyone bought/used it?
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Old October 11th, 2006, 16:24   #4
pghPAtdi
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How does this place compare in price to what you have seen?
http://www.import-catalytic-converte...rter-warehouse

219.00 bucks seems pretty reasonable. Or you could stick a paint mixer spade in there on a drill andbeat the he11 out of the inside.

Dave
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Last edited by pghPAtdi; October 12th, 2006 at 12:47.
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Old October 12th, 2006, 08:44   #5
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I think you would be better off trying to find a salvage car, there are a couple being parted out in the For Sale section, and get the exhaust from that.

I don't know how feasible this is, but disconnect the exhaust, stuff some heat shielding around the turbo outlet and see if the actual and requested come more into line.
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Old October 13th, 2006, 06:02   #6
Mikey2
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The CAT on a diesel car is not something you truly need and it will not affect measured exhaust values.

Remove the CAT and using a length of steel bar remove the fillings inside the CAT and reinstall it. That is a standard procedure by VW dealership in Finland !
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Old October 13th, 2006, 06:19   #7
Doug Huffman
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I wonder how 'stealership's no-service department' is said in Finnish?
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Old October 13th, 2006, 10:58   #8
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Quote:
Originally Posted by Mikey2
The CAT on a diesel car is not something you truly need and it will not affect measured exhaust values.

Remove the CAT and using a length of steel bar remove the fillings inside the CAT and reinstall it. That is a standard procedure by VW dealership in Finland !
This rare (and oft difficault to locate) "tool" is refered to as a "Devil's tooth pic". I have one such tool. I've used it a few times....works well.
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Old October 13th, 2006, 12:55   #9
veget8
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Well, I just got the car back from the muffler shop. Incidentally, they said they were required by law to replace a catalyst on a vehicle that has one from the factory. Had them replace the cat and do a mufflerectomy (I don't want any variables left). They used a high flow cat designed for a diesel, not sure what brand.

Took the car for a test drive and the only thing different is that it's louder. Top speed is still around 75-85 depending on whether I am going up or down hill. Power is fairly good until about 2800 rpm, and then it drops off pretty quick. The car won't go past much past 3200rpm in any gear, if it does, it creeps by it. If I jump hard on the pedal in first there is a quick puff of black smoke around 2000 rpm.

Thanks for everyone's suggestions anyway. I was pretty sure this was going to be it.
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Old October 13th, 2006, 21:42   #10
chromeBuddha
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So are we looking for a boost leak or a really stuck VNT at this point?
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Old October 15th, 2006, 20:04   #11
veget8
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FYI, This thread has been taken over by http://forums.tdiclub.com/showthread.php?t=155184
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Old October 15th, 2006, 20:24   #12
whitedog
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Quote:
Originally Posted by HERM
You'll need a diesel CAT.
Just not a Cat diesel.
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Old October 18th, 2006, 09:51   #13
cattlerepairman
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Default Are You Sure...

..that the "new" MAF was not DOA?

I would, at this point, replace it with a known good one (from a TDI that runs like the bat from hell, compared to yours) and see if that makes a difference. The values you posted and the drop-off at 2800 rpm sound too close to a bad MAF for comfort.

A good MAF meets the 800 - plus requested value without problems and can measure a flow of over 1000.


Quote:
Originally Posted by veget8
Well, I just got the car back from the muffler shop. Incidentally, they said they were required by law to replace a catalyst on a vehicle that has one from the factory. Had them replace the cat and do a mufflerectomy (I don't want any variables left). They used a high flow cat designed for a diesel, not sure what brand.

Took the car for a test drive and the only thing different is that it's louder. Top speed is still around 75-85 depending on whether I am going up or down hill. Power is fairly good until about 2800 rpm, and then it drops off pretty quick. The car won't go past much past 3200rpm in any gear, if it does, it creeps by it. If I jump hard on the pedal in first there is a quick puff of black smoke around 2000 rpm.

Thanks for everyone's suggestions anyway. I was pretty sure this was going to be it.
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Old October 20th, 2006, 18:54   #14
veget8
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Quote:
Originally Posted by cattlerepairman
..that the "new" MAF was not DOA?

I would, at this point, replace it with a known good one (from a TDI that runs like the bat from hell, compared to yours) and see if that makes a difference. The values you posted and the drop-off at 2800 rpm sound too close to a bad MAF for comfort.

A good MAF meets the 800 - plus requested value without problems and can measure a flow of over 1000.
Cattle-

Thanks for the suggestion. I have tried several MAFs that I had on hand, but I haven't really had one that I knew was right out of a working car. I will keep an eye out for someone who would be willing to let me try theirs. Thanks
-Scott
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Old October 30th, 2006, 17:08   #15
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Your turbo maybe going south. Have you checked or replaced the fuel filter?
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