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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 February 21st, 2019, 12:08   #1
p930man
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Join Date: May 2007
Location: Rosharon, Tx
Fuel Economy: jetta 40-50
Default Weak or dead turbo?

Hello folks, I just picked up a 2002 Jetta. 237 k miles, 5 speed standard.
I picked it up at a good price, the previous owner thought he had a dead turbo. I was not so sure so I pulled the trigger. No code now, probably need it to cycle. I have a ZURICH code reader, pretty good reader. The only thing I see is a #1 glow plug is dead. No problem. I checked the vacuum lines using a generic diagram, replaced many bad lines and checked routing. All seems to be okay now, maybe??? The turbo will boost fine about 5% of the time, the rest of the time SHE ACTS DEAD. I have a hard time getting her above 3000rpm, but sometimes she comes alive and runs normal, 80mph easy. I know I need to give you some codes, but don't have them yet. Being a stupid idiot that I am, I tried hooking the vacuum from the vac pump directly to the actuator valve on the turbo. Nothing! I sucked on the actuator hose to see if the diaphragm was bad, it appears that it will hold the vacuum. I'M thinking maybe the actuator is not opening the waste gate allowing the turbo to spool. But sometimes it does, folks i'm a tad perplexed.
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Old February 21st, 2019, 12:23   #2
gforce1108
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First - there is no wastegate.... Second - there are some really good how-to testing threads (search limp mode) that will guide you through a step by step.

This is one that will work:
http://forums.tdiclub.com/showthread.php?t=179589
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Old February 21st, 2019, 12:31   #3
BobnOH
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Actuator is a good place to start, pretty common for cars that age.
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Old February 21st, 2019, 12:50   #4
Tdijarhead
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Might just be sticking vanes.


These little levers control the vanes. They get gummed up and don't work freely. Some try oven cleaner but the best way to clean a turbo is to pull it apart.




Last edited by Tdijarhead; February 21st, 2019 at 12:55.
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Old February 21st, 2019, 13:36   #5
p930man
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After removing the verbal boot out of my butt. I took G forces advice and read the treads. Thanks G force, GREAT advice and information. So far I unplugged the MAF,she is running better, may be 50% boost, still a dog but a big dog. I'll recheck my vacuum lines and be prepared to buy a new MAF. I'll check the actuator, but I think it probably is okay. Then if needed I will pull the turbo and check the vanes. Thanks guys, as always your the best. I'll get back with my results, my cel is on probably because I unplugged the MAF
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Old February 21st, 2019, 15:03   #6
WildChild80
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Have you considered a stopped up intake?

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Old February 24th, 2019, 19:03   #7
p930man
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UPDATE!!! Just wanted to give everyone an update. Pulled the plug on the MAF, she seemed to run better. Tripled checked and replaced leaking and torn vacuum lines. Pulled EGR, clean and removed a bunch of carbon out of intake. Tried cleaning the MAF, didn't seem to help, ordered a new one. Checked vacuum at different connections, we are getting sufficient vacuum. Ordered complete vacuum line set. N75 valve does not seem to modulate the vacuum going to the actuator, and it does not click, its appears to be straight vacuum non modulated. Ordered a new n75 valve. My last question is this car, use to be an automatic, it is now a standard, I can feel the detente on the accelerator, passing gear type feel. Does the ecm need to know that this is now a standard, and can this be affecting the turbo spooling. I did not do the swap, it was done by the previous owner and he claimed it cost him 3,500$ to do the swap. Just pulling things out of my butt at this time. THANKS GUYS
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Old February 24th, 2019, 19:22   #8
Rrusse11
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Does the ecm need to know that this is now a standard?

Yes! You can do it with VCDS.
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Old February 25th, 2019, 13:44   #9
p930man
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Thanks Rrusse, interesting, I'm not saying it was not done at the swap, but I don't know. I have ordered everything else, MAF, N75, VACUUM LINE KIT, the vacuum pump seems to produce sufficient vacuum, so I did not order that. The lines are all good now, but its a bit of a rats nest. NAPA, charged me $40 bucks for vacuum line and connectors, you know Ill never do business with them again. My map sensor seems to read 30, doesn't seem to change, I assumed that is probably okay, Im using a ZURICH code reader, pretty good, BUT????. As I sated in my previous post, the N75 is allowing full vacuum to go to the actuator, no modulation and no buzz so I assume it is bad, now I should a checked the plug to make sure it was energized. I sure hope I didn't waste $50 on the new one I ordered, DAMN! I recently had to send my ECU on my 06 out do to fix a cel code, where the actuator was not talking to ecu. A gentleman in Dallas reprogrammed the ecu and fixed the problem, but it cost me about $500, labor, shipping. I like this this little bastard, but I don't want to spend the bank account on her. Can a local Guru check the ecu compatibility with the manual transmission?
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Old February 25th, 2019, 15:20   #10
Rrusse11
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p930man,
All's you need is someone with a RossTech cable, and a laptop with the free VCDS software. Should be someone in the neighborhood.
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Old February 28th, 2019, 19:29   #11
wonneber
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If you tee a vacuum gauge into the line going to the actuator you should see about 10 inches vacuum at idle.
It should drop when you drive away.

A vacuum pump is more useful, it can check if the actuator (and other things) is holding vacuum.
There's a VW bulletin about the actuator's rusting internally. It has to be removed to check it.
2 nuts, the vacuum line, and a e-clip.
Tie thread or dental floss to the clip so if it flies when you try to put it back on it's easier to find.

While the actuator is off move the arm going into the turbo full range to see if it moved full range freely and does not stick.
I've read some have worked it for 5 minutes to free it up.

In the long run VCDS is more then a scanner and can be used to diagnose problems.
VCDS lite software is free but you need a laptop & OBD2 cable that works with it.

You should buy Bosch electronics for the computer sensors & such.
Many have had issues buying cheap China parts.
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Old February 28th, 2019, 20:46   #12
Rrusse11
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"NAPA, charged me $40 bucks for vacuum line"

And they probably gave you the wrong hose. Just rubber?
You really want the Gates cloth wrapped line like this;


https://www.idparts.com/3mm-idvacuum-hose-p-620.html
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Old March 3rd, 2019, 11:35   #13
AndyBees
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Quote:
Originally Posted by p930man View Post
I tried hooking the vacuum from the vac pump directly to the actuator valve on the turbo. Nothing! I sucked on the actuator hose to see if the diaphragm was bad, it appears that it will hold the vacuum. I'M thinking maybe the actuator is not opening the waste gate allowing the turbo to spool. But sometimes it does, folks i'm a tad perplexed.

When the engine is started, Vacuum pulls the Actuator arm down solid against the adjustable set-screw. It stays there during idle... release of vacuum by the N75 Valve results in the Actuator Spring pushing the arm up and away from the set-screw ................. Hmmm most people think "vacuum" controls boost.., It's actually just the opposite. Releasing vacuum determines boost. That spring in the Actuator is extremely strong and will push faster than the vacuum pump or stored vacuum can pull against it.

The above is extremely easy to observe looking up from the bottom on the ALH engine in my Vanagon.

And, as others have stated........... No Waste-gate in the VNT Turbos.. just changing the angle of the Vanes that "direct" exhaust gasses across/over/thru the Blades of the Turbo...

You need to get the DTCs...
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Old March 3rd, 2019, 16:49   #14
wonneber
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Quote:
Originally Posted by AndyBees View Post
Hmmm most people think "vacuum" controls boost.., It's actually just the opposite. Releasing vacuum determines boost. That spring in the Actuator is extremely strong and will push faster than the vacuum pump or stored vacuum can pull against it.
It's always confused me because if you to not have vacuum you don't have boost.
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Old March 3rd, 2019, 16:50   #15
WildChild80
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Quote:
Originally Posted by AndyBees View Post
When the engine is started, Vacuum pulls the Actuator arm down solid against the adjustable set-screw. It stays there during idle... release of vacuum by the N75 Valve results in the Actuator Spring pushing the arm up and away from the set-screw ................. Hmmm most people think "vacuum" controls boost.., It's actually just the opposite. Releasing vacuum determines boost. That spring in the Actuator is extremely strong and will push faster than the vacuum pump or stored vacuum can pull against it.

The above is extremely easy to observe looking up from the bottom on the ALH engine in my Vanagon.

And, as others have stated........... No Waste-gate in the VNT Turbos.. just changing the angle of the Vanes that "direct" exhaust gasses across/over/thru the Blades of the Turbo...

You need to get the DTCs...
The logic is sound but when I had a massive vacuum leak at the brake booster line, it wouldn't make boost at any RPM or throttle position, could it have been the vanes were too far advanced and in essence stalling the turbo?

Andy, I know you've been in and out of these engines and trust your knowledge, but I've gotta see this... hopefully tomorrow I can hook the mighty vac to the turbo actuator line and watch it...to think of it I've only heard of the test to check the movement but never how it actually worked. This is intriguing.

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