Narrowing down low power causes

eddieleephd

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Battle Ground, Wa
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2002 jetta Wagon
Highway driving's a bit more than I would recommend for disconnection of down pipe while driving, however, I still think it's the cat. The improvements you are speaking about can be caused by the he cat warming up and burning out some of the soot and oil in it.
ktmkris had a good idea for checking the cat with an ir thermometer.
I was having similar issues. My catalytic converter was melted. Power was all over the place. To test it on my car I unscrewed oxygen sensor and drove it. The little bit of extra flow makes a difference. The other thing you can do is measure front cat temp and rear cat temp. Just get a cheap ir point and shoot thermometer. Good luck to you.

So you believe the turbocharger cleaning helped?
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WildChild80

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May 30, 2016
Location
Nashville, AR
TDI
2001 Jetta TDI 2000 Jetta TDI 2000 New Beetle TDI ALL 5 speeds
Highway driving's a bit more than I would recommend for disconnection of down pipe while driving, however, I still think it's the cat. The improvements you are speaking about can be caused by the he cat warming up and burning out some of the soot and oil in it.
ktmkris had a good idea for checking the cat with an ir thermometer.

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I agree, seems to be a cat issue...maybe more problems maybe not but seems the cat is your biggest at the moment.

I recommend getting the cat and go from there.

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eddieleephd

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Location
Battle Ground, Wa
TDI
2002 jetta Wagon
Another option is to remove and attempt to clean with super clean degreaser to remove oil and soot.
You can tell a lot when doing this, if you clean one that's not so dirty it will run virtually clear on the second flush.

Fill with full strength cleaner and wearing gloves slosh back and forth side to side to get everywhere inside. The running of fluids takes a little longer through the medium, but, cleaner should make it through inside of 45sec. Also, how much will fit inside will tell how clogged it is.

This method ultimately is avoiding the inevitable, however, catalytic converters were always considered cleanable and reusable until we got into the throw away mentality and everything is disposable, for temporary use.

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WildChild80

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2001 Jetta TDI 2000 Jetta TDI 2000 New Beetle TDI ALL 5 speeds
I had wondered if you could clean it, I've never heard anyone talk about it from big dealerships to some sketchy shade tree shops but it's worth a try, worst case you end up gutting it and you're really not out much but time and some cleaner.

If the Platinum inside is fused you're toast...

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eddieleephd

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May 27, 2012
Location
Battle Ground, Wa
TDI
2002 jetta Wagon
I had wondered if you could clean it, I've never heard anyone talk about it .

If the Platinum inside is fused you're toast...

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Good ole' boys from the railroad told me lots of the original things.
Unlikely if it's clogged that platinum, what you clean, would be fused. Not that I'm calling it impossible.


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WildChild80

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2001 Jetta TDI 2000 Jetta TDI 2000 New Beetle TDI ALL 5 speeds
Good ole' boys from the railroad told me lots of the original things.
Unlikely if it's clogged that platinum, what you clean, would be fused. Not that I'm calling it impossible.


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Diesels are different and soot is certainly way more cleanable than whatever builds up in gassers. It actually makes sense

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2000alhVW

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Aug 30, 2018
Location
Silver Spring, MD
TDI
2000 Golf
I was having similar issues. My catalytic converter was melted. Power was all over the place. To test it on my car I unscrewed oxygen sensor and drove it. The little bit of extra flow makes a difference. The other thing you can do is measure front cat temp and rear cat temp. Just get a cheap ir point and shoot thermometer. Good luck to you.

So you believe the turbocharger cleaning helped?
Do these cars have oxygen sensors? I never really thought about it, but I've ever seen any sort of data reading or graph in VCDS to monitor O2 sensor readings. Odd, since that's a pretty important data collection point for gassers.
Additionally, I just looked at Rockauto, and I can't find any listing for Oxygen Sensor, and none of the exhaust components have cutouts/bungs for O2 sensor installation.

I'm not confident my novice effort to clean the turbo netted any benefits. My turbo vanes were extremely 'loose'. You could practically move the VNT lever by blowing on it. No notchiness, or stickiness anywhere in the range, extremely smooth, etc. The turbo also looked pretty good when I peaked in the exhaust side as well.
I feel like the progression of my issue (moving from perma-limp-mode to having some power) is nearly 100% due to my adjustment of the actuator rod.


So, I'm back for the week, and want to make a plan to finally put this issue to rest.
What do you think my plan of action should be?

I have used a household vacuum clean to pull a vacuum through the exhaust. It seemed to flow fine, but I understand this is low air volume.
Is there an oxygen sensor? Or perhaps an oxygen sensor port covered with a block-off plate I could open up to create additional airflow?
Or is the best plan of action simply to 'go all the way' and pull off my cat hoping the fasteners aren't too rusted
 
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BobnOH

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May 29, 2004
Location
central Ohio
TDI
New Beetle 2003 manual
No oxygen sensor.
I would back up and find a step by step troubleshooter, here or myturbodiesel have good ones. We're almost up to 100 posts of interweb guessing. Sounds like you're familiar with the bits involved, you'll find an answer soon.
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2000alhVW

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Aug 30, 2018
Location
Silver Spring, MD
TDI
2000 Golf
Found posted in another thread

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Thanks for the link. I acknowledge Scotty is helpful, but I can't get over his hand gestures. Him pointing at the camera every 5 seconds makes me cringe.

I may look into it, but I'm not sure. My car keeps driving better and better :confused:


I think the engine as gotten good enough that the transmission is the new area of concern. Just an 01m being an 01m.

Updates with the engine: I drove back from school on Thursday night. More often than not, I was 'in the boost'. There were 5-6 occasions I couldn't 'find the boost' and had to shove over to the shoulder, but I was able to keep on the boost for sometimes as long as 15 mins. I kept on light throttle, and just pressed harder when I needed it.

Also, the throttle-to-power ratio on this car is bonkers. When I'm in the boost, there's no stopping this thing. Even at 20% throttle (or what feels like 20%), this thing just blasts up the hills. It almost becomes a cycle: catch the boost, accelerate to 70, 75, 80, 85 "oh crap, let me slow down", ease off throttle, car keeps accelerating, "I don't want to let OFF the throttle, and lose boost, but it keeps going" so then I go to 0% throttle, slow down to ~70mph and repeat.
Also, halfway through the trip, it rained with a huge temperature drop. The car gained noticeably more power, due to improved intercooler abilities, I assume.

I accidentally tailgated so many cars simply trying to maintain ~15% throttle.

So, this whole time, I've been using an OEM Bosch MAF that was removed from an NB in the junkyard. When comparing requested vs. actual MAF values, it was pretty good. The one issue I could see is that the MAF rarely reported above 750, and only saw it at 790 once. Also, the car choked out at ~4000rpm.

I swapped in my eBay "Bosch" MAF, and I noticed some strange things. The car runs better! Previously it was at 80%, but now I think like 90-95%. I can actually floor it from 0mph, and it goes. It 'stays in the boost' all the way, even through gear shifts.
One thing that worried me - I've seen the MAF report 930 (!), when the max requested value I've seen is 850.
Is this okay....?

Also, I put the shifter in 1st (auto trans), and wanted to re-test 4000rpm choke point. My gauge cluster shows a redline of ~4700 (?), but the car revved up to ~5000-5100 without stopping. I left off the throttle, but it caught me off guard. Is there no sort rev-limiter like on gas cars?
For now, I think the engine is okay enough for me to drive as is, but my next highway trip will confirm.
 
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eddieleephd

Top Post Dawg
Joined
May 27, 2012
Location
Battle Ground, Wa
TDI
2002 jetta Wagon
Time to do some boost logging. Only way to answer your maf question.

The cat will burn out the stuff inside if it gets hot enough. Faulty maf definitely falls in line with your issue.
The Rev limiter is your foot.
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