Narrowing down low power causes

eddieleephd

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What would this mean though? I'm understanding it to mean that very gradual changes in boost command (driving very gently and light throttle) would cause overboost. But driving more aggressively wouldn't?
This all really depends on what's actually going on.
From your last post it seems like the actuator could be bad in the vacuum side and leaking itself.
This could have been caused by the turbo.
Before you easy off it remember to feel for play on the turbo shaft. This would tell you if you want to begin looking for a new one.
If the shaft has sideways movement the bearings are going.
I also say to check for any leaks in the return and supply lines, supply lines are highly suspect for issues.

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eddieleephd

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"I kinda assume the computer would either freak out and retreat to limp mode, or just go off of a pre-determined middle-of-the-road value such as when the MAF is unplugged and it simply uses 550 for all calculations."
This is exactly the point, when you pull the plug it uses default values and if there is an improvement the maf becomes suspect.
Overboost isn't affected by pulling the maf, the boost sensor still sees what it sees.

I honestly think the turbo is suspect, at least the actuator. If the actuator won't hold vacuum it can't modulate boost correctly. If the lever is worn and that's causing the issue, easy off won't be able to make it better.
You can limit the range of the actuator with adjustment of the set screw and possibly stop it from getting to the sticky spot to get you by for a bit.

I had an overboost caused by the lever being extremely worn on a 300,000mi turbo, within 15 anyhow. I upgraded to a VNT17 and then had an overboost caused by misadjustment.


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2000alhVW

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"I kinda assume the computer would either freak out and retreat to limp mode, or just go off of a pre-determined middle-of-the-road value such as when the MAF is unplugged and it simply uses 550 for all calculations."
This is exactly the point, when you pull the plug it uses default values and if there is an improvement the maf becomes suspect.
I had actually written an additional paragraph to that post, but deleted it.
It went like:
According to the Limp Mode 101 thread around here, the #1 item on the list is suspect of a bad MAF. It says "unplug MAF. If car runs the same, or improves, then the MAF is bad. Replace!"
Additionally, you can verify this visually via VCDS actual vs. requested MAF data.

But this isn't accurate, at least not in my situation. My MAF was reporting depressed airflow values because real airflow was restricted. The MAF was/is reporting accurately. The reason that airflow is low is because the turbo isn't turbo-ing because the computer cut all boost and fuel.
Same with a gunked up I/M, for example. If air can't flow, then MAF would report ~400. But if you unplug MAF, and the computer uses the 550 baseline, then power would improve!

I've given this exact troubleshooting procedure a lot of thought over the past few weeks, and I'm disappointed. It's a bad test and it proves nothing. I've tested a total of 3 MAFs (2 OEM Bosch, 1 of which brand new) - all report identical values under all circumstances, but my car runs 10x better with MAF unplugged.
 

WildChild80

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From what I've read, if you unplug the MAP not MAF it will go into limp mode. I don't think it has a default boost map to use in the absence of the MAP input, again that's speculation based on what other people on various forums have talked about.

I second taking a good close look at the turbo first, figure out why the actuator isn't moving like it should and make sure what's left is worth working on. With the lack of oil in the intercooler, I'd feel pretty confident that the cartridge is still good but still worth checking while you're in there

Did you hook up straight to the actuator and watched it leak down? If you have a leak you have a bad actuator, there may be other stuff wrong but if it's leaking that's your first problem. I might have a good actuator if you need and can wait for USPS

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2000alhVW

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From what I've read, if you unplug the MAP not MAF it will go into limp mode. I don't think it has a default boost map to use in the absence of the MAP input, again that's speculation based on what other people on various forums have talked about.

I second taking a good close look at the turbo first, figure out why the actuator isn't moving like it should and make sure what's left is worth working on. With the lack of oil in the intercooler, I'd feel pretty confident that the cartridge is still good but still worth checking while you're in there

Did you hook up straight to the actuator and watched it leak down? If you have a leak you have a bad actuator, there may be other stuff wrong but if it's leaking that's your first problem. I might have a good actuator if you need and can wait for USPS

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I tested the actuator in many different ways. I've repeatedly hooked up directly to the vac line with a hand pump, but I've also watched the rod actuate on engine start up.
When I said it was leaking vacuum, I mean that this particular vacuum hand pump setup was leaking at one of the fittings as I have to use a couple of adaptors to go from 3mm vac line to the MityVac nipple
 

WildChild80

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Ok.

Let's summarize what you've verified

Actuator good
Vanes move as they should
No boost leaks
Good MAF
Good vacuum pump

Aside from an air leak pre turbo or a MAP sensor is there anything else it could be?

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2000alhVW

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Ok.

Let's summarize what you've verified

Actuator good Actuator holds vacuum perfectly. Rod possibly ill-adjusted. Set screw as well. Have not checked with feeler gauge. Acuator could have internal issue with slow retraction
Vanes move as they should Have not removed actuator clip to test vanes independently. When moving vanes via actuator, no binds or jumps
No boost leaks Cannot confirm for sure. I am skeptical of boost leaks as I have seen VCDS report semi-extended periods of 1500+ mbar boost. I have inspected accordion intake pipe, and plastic pipe from PCV to turbo. Inspected 90 degree rubber hose to EGR. Inspected rubber hose from turbo via hand. Everything else could be questionable.
Good MAF Have used 3 different MAFs (2 are OEM Bosch, 1 of which is new) which all report identical values/performance.
Good vacuum pump 25+ inHg at idle.

Aside from an air leak pre turbo or a MAP sensor is there anything else it could be?
Fuel issues, ECU is broken or FUBAR'd via prior VCDS tinkering. Exhaust?

To recap, everything I've done:
  • Bought Bosch OEM MAF off eBay for $40. Car had new looking no-name MAF. Snagged unknown Bosch OEM MAF from a junkyard car that matched eBay MAF.
  • Replaced all vacuum lines. Checked and re-checked routing.
  • Replaced PCV valve, pipe, and grommet.
  • Replaced fuel filter
  • Replaced air filter and cleaned snow screen
  • Checked check-valve (only 1 check valve, correct?)
  • Checked wobbly tube from vac pump up to brake booster
  • Cleaned I/M and EGR valve. Replaced gaskets.
  • Swapped out N75 with N18, donor N75 and donor N18
  • New 109 relay
 

WildChild80

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Either you have a vane issue or...

I'm starting to think catalytic converter or exhaust issue.

Does your donor car still have a cat? If it does you could get the cat and swap down pipes and see if that helps

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eddieleephd

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Either you have a vane issue or...

I'm starting to think catalytic converter or exhaust issue.

Does your donor car still have a cat? If it does you could get the cat and swap down pipes and see if that helps

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X2 on the cat here.

You can simply disconnect the down pipe and try that before swapping to ensure it is worth swapping out the cat.

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eddieleephd

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You're saying drive the car with the downpipe disconnected?
Yes, that would tell you if the issue is the exhaust. Not saying that you should go across country, just take the nuts off and drive it to see what happens.
If everything is normal, yet loud and ballsy, you need a cat at minimum and should review the rest.

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WildChild80

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You're saying drive the car with the downpipe disconnected?
I wouldn't, there's a lot of heat that comes out of the turbo and you'll melt something or catch something on fire...now if you had the down pipe and cut it right in front of the cat you'd be fine

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eddieleephd

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You're telling me that driving down the block with the down pipe separated is going to cause damage?
In the end loosening the nuts so there's a gap and no back pressure would be all I need to get what I need to know if the exhaust is causing the issues.
Not a road trip to California, 500 feet, and there's other precautions if you're that worried, a heat shield of some sort maybe.
As soon as you put your foot into it you should feel the difference.
The intake is back there so loosening the nuts causing it to go up wouldn't be good.
Put a wedge at the bottom and tighten the top to force the exhaust down and out.
I wouldn't, there's a lot of heat that comes out of the turbo and you'll melt something or catch something on fire...now if you had the down pipe and cut it right in front of the cat you'd be fine

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WildChild80

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You're telling me that driving down the block with the down pipe separated is going to cause damage?
In the end loosening the nuts so there's a gap and no back pressure would be all I need to get what I need to know if the exhaust is causing the issues.
Not a road trip to California, 500 feet, and there's other precautions if you're that worried, a heat shield of some sort maybe.
As soon as you put your foot into it you should feel the difference.
The intake is back there so loosening the nuts causing it to go up wouldn't be good.
Put a wedge at the bottom and tighten the top to force the exhaust down and out.

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What's wrong with that statement is that the flange doesn't move any way you want it to. In order to get enough space to actually make a difference you wouldn't be able to keep the gasses from going everywhere.

If you had ever pulled a down pipe off you'd know you have to almost pull it straight off to get it off the studs, you might get 1/2 inch Gap at most...the other end is hooked to a flex pipe that has a dual pin rubber mount on it and it doesn't move that easily.

But then there's that thing called exhaust gas temp gauges made famous by diesels because turbo gas cars don't have to worry about the temp like diesel engines do. When the EGT rises it's in response to an already hot gas situation. And what is the purpose of this test? To make power...in the diesel world, power and heat go hand in hand...so when he tries to make power he's gonna get a stream of 600 to 1200 degree gas...news flash, plastic and rubber melt far south of the low number and there's a ton of it in that area...


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eddieleephd

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We all have our ways and not everyone should try mine.
Play your way and fight with the down pipe for 3 hours to see if it changes anything.
I will take it loose and bend some of the metal roofing sitting 20 feet over there to act as a heat sheild and see what happens with the exhaust separated. In 15 minutes I will know if it's worth swapping out the cat and if it will solve the issue or not.

Assuming you have any idea what I have done as far as the down pipe goes is ludicrous. My engine is sitting on the ground and my freshly cleaned down pipe is sitting in place with my recently installed egt bung 90mm from the turbo outlet. Next I'm going to be doing a cat back and welding it rather than fighting with that clamp and the midsection I can't seem to get enough leverage on to push into the clamp.

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WildChild80

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That clamp sucks, I fought one once, the next time I ripped it off and replaced it then sold the car. The stainless clamps on my 3 inch turbo back are nice.

The last time I was in the salvage yard I took a down pipe home... glorious because they chopped the cat off for me.

Why didn't you mount your EGT bung pre turbo? Your temps are gonna read lower than pre turbo...my turbo was pre drilled and threaded when I bought it

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WildChild80

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We all have our ways and not everyone should try mine.
Play your way and fight with the down pipe for 3 hours to see if it changes anything.
I will take it loose and bend some of the metal roofing sitting 20 feet over there to act as a heat sheild and see what happens with the exhaust separated. In 15 minutes I will know if it's worth swapping out the cat and if it will solve the issue or not.

Assuming you have any idea what I have done as far as the down pipe goes is ludicrous. My engine is sitting on the ground and my freshly cleaned down pipe is sitting in place with my recently installed egt bung 90mm from the turbo outlet. Next I'm going to be doing a cat back and welding it rather than fighting with that clamp and the midsection I can't seem to get enough leverage on to push into the clamp.

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Hammer worked for me...just tap it into place...the bolts we're rusted out on mine, used nuts before I replaced it

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2000alhVW

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After a 2 hour struggle, I got the downpipe off. No way, in my opinion, to get the top 2 nuts off from the bottom without a lift and a really long 12mm wrench. Seems every time I work on this car, it's a 6 hour affair, so I decided to preemptively remove the intake manifold instead of tearing my arms up THEN removing the I/M.

My EGR valve is 100% as soot'd up as it was before I cleaned it down to the shiny metal. ~800 miles put on it since the cleaning...Interesting.

I also tried to mess with the actuator. Holy crap. Rounded one of the two nuts ON the actuator, and completely rounded one bolt on the actuator bracket. Gotta love it.

Here's the best part! I got the actuator rod off (circlip instantly disappeared into thin air, of course). Literally. Not even a far away *ting* letting you know that if the blood dripping down your arms, oil/grease on your face, and your aching back from staying bent over for 2 hours straight has made you delirious enough to engage in such shenanigans, then there's a game of "find the needle in the haystack" waiting for you when you're done!

Without further ado, here's what I found:
https://www.youtube.com/watch?v=eFXY5o86-uM
https://www.youtube.com/watch?v=7GZfyrt_ZSo
 

2000alhVW

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Turbo looked and felt pretty dang good. But I did the whole Easy-Off spray for good measure, and since I already had the DP off.

I've got the whole intake apart. How can I test the exhaust for clogs?
 

eddieleephd

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That's difficult due to volumes. You can clean it up and it works fine. I just used super clean and stuck it back on.
Could try a wet dry vacuum and see what it does. You Know absolutely if it works hard it's clogged, probably 30cfm or I'm guessing.

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WildChild80

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Would the actuator hold vacuum?

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WildChild80

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Do an EGR delete and don't look back...it makes everything work related on the back side of the engine possible and even borderline easy.

There's many places to get those clips, a hobby shop will have them or harbor freight.

Does your system hold vacuum? Take the line off the vacuum bulb and pull it down with the mighty vac after you address the ASV nipple fixed that is

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2000alhVW

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Do an EGR delete and don't look back...it makes everything work related on the back side of the engine possible and even borderline easy.

There's many places to get those clips, a hobby shop will have them or harbor freight.

Does your system hold vacuum? Take the line off the vacuum bulb and pull it down with the mighty vac after you address the ASV nipple fixed that is

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strongly considering it. Occasionally I'll look up pros/cons of the EGR delete so I know what I'm doing. It seems like the pros are no more carbon build up, and the cons are just slightly more emissions?
I'm also not clear on the CEL situation. Can that be coded out via VCDS? If not, will it cause ECU issues to stay on?
Is it as easy as 2 block off plates?


UPDATE:
Sprayed the turbo liberally with Easy-Off. I put the vacuum cleaner in one outlet of my muffler. Obviously, it just took the path of least resistance, and sucked through the other outlet. I got clever and put a piece of cardboard over it. PERFECT SEAL! I walk to the engine bay, and air is freely being sucked through the flex pipe. Seems perfect to me.

I also sprayed Easy-Off and some water down the EGR outlet on the exh. manifold. I filled a spray bottle with water and did ~7 sprays.
About 5-6 hours between spraying Easy-Off and running the motor.
If water did get into the cylinders, it would leak down into the crankcase eventually, no?

I put everything back together and the car is running very odd. The very first start was irregular, and it had a choppy idle. I thought it was similar to Seafoam through the I/M with a gasser.
I pull out of my driveway, and the car is going like 3mph. I tried to drive it for 5 mins, and something is obviously wrong.
It idles pretty normal, but absolutely will not rev above 1500. Approaching 1500rpm, it stutters a lot.


Last question of the night: How do I know if I hydrolocked muh modur?


lol, wouldn't that be ironic. Dick around with this car for 6 months straight. Going through every item on the list, twice over. I finally figure out it's the actuator rod being out of adjustment, and I ruin the motor trying to clean a turbo that wasn't dirty.
 
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WildChild80

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2 block off plates the "race pipe" and coolant bypass.

Doubtful on more emissions to really speak of but some notice or think they notice slower warm ups in the winter. I've got a tuned EGR deleted car and a stock EGR minimized car and can't say I notice much of a difference in warmup time. I've read stories or the EGR cooler failing and dumping the coolant out the exhaust and with it deleted you can't soot up your intake. There are some that will say it took almost a normal cars lifetime to clog so it shouldn't need to be cleaned again blah blah blah.

How did you fix the anti shudder valve nipple issue?

Hydra locking is usually a fairly violent evolution and doubtful you did. You could do a compression test and you should see 1 or more cylinders lower on compression to absolutely rule it out. Harbor freight supposedly has a pretty good tester for diesles.

Pretty sure I've read that 01 and older don't have as much of an issue with CEL after egr delete as the 02 and on. You leave the solenoid plugged in and route the vacuum away from it and change the EGR field in VCDS to 33768 instead 32768. Or if you were to get a tune, Malone has a dynamic EGR or tune it out all together. They also have a dynamic idle that'll help it warm up.

When you were trying to drive it, did it throw a CEL?

Did you hook all of the vacuum lines back up?
 
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2000alhVW

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How did you fix the anti shudder valve nipple issue?


Did you hook all of the vacuum lines back up?
I did not put the ASV plunger back on. I put a screw in the vacuum hose where the ASV nipple would have gone.
Is this problematic? It did run like a gasser with a horrible vacuum leak, but I thought diesels were immune to that? Especially since the vacuum is artificially produced with a pump.

I'm pretty sure I plugged all the vacuum lines back in but I'll double check.
 

WildChild80

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Vacuum controls the boost on your turbo, if you have a bad vacuum leak you won't make boost and you shouldn't have power brakes either

A screw won't stop vacuum, I've tried...

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2000alhVW

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Fixed it: since removing ASV plunger, the valve was in the closed position. Secured it open, then drove 200 miles home.
In addition to spraying turbo with Easy-Off, I adjusted actuator rod to make it longer. I think this is mainly responsible for my findings below.


I always plug MAF back in after a new fix. At first, no change.
I tinkered with EGR values at red lights. Was 33768, reverted to stock: 32768, and car compensated with 10-20% power increase. Could almost keep up with traffic.

Suddenly I could go 25mph up the hill, and then I could do 30 up the next one. Then I started "milking" the car.
What this means is to be extremely gentle with the throttle. I had VCDS open watching requested vs actual MAF and boost levels.
The issue is, the harder I press on the throttle, the less power the car gives. When gently cruising at 20mph, and requested MAF is ~400, for example, the actual value will be right on. But if you press the throttle too fast, a huge fissure opens. Requested MAF shoots to 850, and actual MAF nosedives to 220-250. The car loses all power, and boost values match MAF values.
BUT
If you're cruising at 20, with 400 on both, and very slowly press the throttle, requested MAF goes to 480, and the actual MAF does too! And boost follows suit!
Every time I "milked" the car, it got better. Suddenly I was feeling mild bits of genuine acceleration, and I was pushing MAF values into the 500s and boost levels in the 1500s.
I call it "milking" because I imagine it like a cow: if you're nice, sweet, and gentle to the cow, it yields lots of milk. But if you start squeezing too hard, the milk dries up.
I had to coax it for power repeatedly. The car would offer a slight morsel of boost, then I would press slightly too hard and be punished. When I lost boost, I would have to 'find the groove' again. Sometimes, it would be as easy as 0% throttle, then gently increasing until "the wave came". Other times, I would have to rush over to the shoulder because I went to 0% throttle and tried 5-10 times with no luck.

I'm driving on the highway, seeing MAF values reach mid 600s and actual boost levels match requested at 1950mbar.
Over the course of 3 hours, the car almost reached full potential. The MAF broke 800 once, and I confirmed 2150mbar boost.
But the car still had a mind of its own. One second, I would be blasting up a hill (WV mountains, btw), 80mph, blowing through 90, 95, hitting 100 up hill in 4th gear, with ~60% throttle.
Then, without warning, my sweet boost juice was yanked away, and I'd have to 'find the groove' all over again. Sometimes one 'throttle reset' would do it, other times I would limp on the shoulder for 30 seconds while everyone passed me again. This isn't limp mode reset, I did not cycle the key in-between boost sessions.

Even though I regained intermittent top end power, there is still absolutely zero acceleration down low. The "milking" and "finding the groove" issue is much worse at low speeds. 0-60 is non existent.

It seems completely random. There were times I was maintaining 80mph on flat ground, as steady throttle as possible, and out of nowhere - BAM, all power is lost, and I scramble to the right lane.
 
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ktmkris

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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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