Still Ironing out the Kinks on my new Purchase

System holds vacuum great. I tested it in multiple spots. Could not force a leak. I also waved around my propane torch cylinder. Nothin’.

I might replace the vacuum lines down the road, but I’m somewhat confident they aren’t the issue.
Actually, it’s kinda funny, vacuum lines are such a popular culprit to point fingers at, but I’ve probably wasted 10-15 hours of my life checking for vac leaks. Never had a single leaking vacuum hose in my entire life of car ownership. 8 years, 120k miles between 10-12 vehicles, the newest of which is currently my 2005 Tacoma.

If you want to give me a specific spot to look more closely, sure, but for now I’m tenpted to continue on the list of “low power” suspects

Editing after I remembered that I did not check the vacuum line going down to the turbo. Will do that later

Right. You check, you're done. Move to the next thing. "Still Ironing out Kinks" covers a lot. As you pinpoint specifics it might be better to start a new thread or better yet recycle one with the exact problem (you can bet there is 1 or a dozen).

You do realize that the TDI vacuum system doesn't exit into the intake, right?
So even though you can clearly see the cracked, deteriorated hoses in your own
photos, you'll wait until they do fail or maybe shed debris into the vac system. OK

What he's saying, I thought the same thing, is squirting gas on the lines will not rev the motor in many of the vacuum tube runs.

BobnOH said:

Smaller photos or thumbnails please.
You're on the right path. The diagram at the top is for a car withe the EGR is removed. Try this link
The N75 and the N18 are nearly identical, in fact they can be swapped for diagnosis purposes. The N75 is the one that has a line down to the turbocharger.
Often these cars keep their factory clothe covered vacuum tubes past their useful life. I can't tell if yours have been replaced. The cloth can be fine, but the rubber can be deteriorated.
Here is a user contributed search engine you may find useful (use the search field near the center)

Click to expand...

Yeah i apologize about the photos. I tried 2 other formats and they didn't work. I tried another format and it came out like this. I'll try again.
Thanks for the link to the other vacuum tubing diagrams. Helps a lot. I realized right after I posted that it said "for EGR removed cars" at the top. Seems weird that particular diagram is the one that's so easy to find.

BobnOH said:

Right. You check, you're done. Move to the next thing. "Still Ironing out Kinks" covers a lot. As you pinpoint specifics it might be better to start a new thread or better yet recycle one with the exact problem (you can bet there is 1 or a dozen).

Click to expand...

I tried to change the title. Will try again.

flee said:

You do realize that the TDI vacuum system doesn't exit into the intake, right?
So even though you can clearly see the cracked, deteriorated hoses in your own
photos, you'll wait until they do fail or maybe shed debris into the vac system. OK

Click to expand...

Factually, I did know that the vacuum system does not go to the intake, but I had forgotten as I'm not familiar with diesels. That's why I asked in a prior thread.
Vacuum tubes are fine, as stated above.

. My first order of priority is to solve the run-ability issue, not to knee-jerk and spend $40 on every slight non-issue that appears

BobnOH said:

What he's saying, I thought the same thing, is squirting gas on the lines will not rev the motor in many of the vacuum tube runs.

Click to expand...

Thanks for clarifying. I was a bit confused for a second.

Fixed pictures.
I guess my next move is to get under the car and look into the turbo more closely.

A couple updates...

I bought MAF cleaner and sprayed the elements of the MAF. At the same time, I plugged the MAF back in as I had been driving with it unplugged for 5-10 miles. CEL immediately on when unplugged MAF prior.
No difference on my short drive home. 1.5mi.

I take it out tonight to investigate more thoroughly and odd stuff started to happen.
I get on the highway, struggling to maintain 60mph.
I have the pedal constantly floored.
Car has low power approaching 2000rpm, press harder on pedal and lose power.
Downshift trans, motor jumps to 3500rpm, no new power.

BUT

I start to throttle the pedal. Floor it, ease off to 60% for 0.5 seconds, floor it again. Each time I press down, the motor gives a small morsel of power. The MPH and RPM creep up in small increments.
Then, suddenly the car launches. Gobs of power. Like there had been a clog somewhere, and it's cleared up.
Unfortunately, I can't keep on it for long because I'm now 75mph and there's traffic.
Let off the pedal, and....it's gone. No power again.
A couple of times, I was able to get back into "Sport mode". It got easier each time. Blip the throttle repeatedly until "VTEC kicks in".

I've also noticed puffs of light colored smoke a few times in the rearview. Seems like a lean condition. I don't know. Still investigating. All new parts have arrived and I've got an appointment with a VCDS soon.

I'm assuming the missing hose on the solenoid in the picture is where you are getting vacuum to the pump.

Tee into the line going to the actuator on the turbo. Start the car and you should get vacuum. (not 20+ inches)
When you take off the vacuum should drop off.

I wonder if the turbo veins are sticking.
You might have to take the actuator shaft off at the turbo arm to move the arm full sweep.

If it's sticky but moving you may have to work the arm back & forth to see if the frees it. Might take 5 minutes working it from what I've read in the past.

wonneber said:

I'm assuming the missing hose on the solenoid in the picture is where you are getting vacuum to the pump.
Tee into the line going to the actuator on the turbo. Start the car and you should get vacuum. (not 20+ inches)
When you take off the vacuum should drop off.
I wonder if the turbo veins are sticking.
You might have to take the actuator shaft off at the turbo arm to move the arm full sweep.
If it's sticky but moving you may have to work the arm back & forth to see if the frees it. Might take 5 minutes working it from what I've read in the past.

Click to expand...

Thanks for the reply. You are right in that assumption.

I got some decent updates. I got access to a VCDS cable.
I replaced the G38 sensor last night and dove into tinkering with everything again.
I took off my vacuum hoses and checked them individually. I found one that had a minor leak, and decided to stop being hardheaded and replace them all. The offender was the incoming hose for the EGR solenoid.
I temporarily replaced it with something better. Also, I tried to test the solenoid and it hold held vacuum in one direction. The other direction was completely open.

I tested the hose on the actual EGR valve. It just hissed, and was pulling air openly from the hose going to the airbox. Is this normal...?
Then I put the vacuum pump onto the long hose going to the actuator. I didn't get down there and measure travel, but I confirmed movement.

Replaced G38. Replaced a bad vac hose.
Went for a drive, got some power back. Still intermittent, but has more power more often. I can actually feel boost now.

Tinkered quote a bit with VCDS. Gotta be honest, it hasn't really offered any diagnostic help so far. All of my diagnostics has come from me sticking my head in the engine bay. VCDS is definitely cool, and I can see how it can be very helpful, but the car just aint throwing any real CEL/DTCs...
I guess it's because it's a 2000, but it's kinda 'dumb'. Lots of options aren't available. Including the "Group 011" for doing the N75 on/off command. No Group 011 available for communication.

Here's some things I found. How bad is this stuff?

subscribed

EGR solenoid will vent to the airbox when the valve is 'off'.
The amount of crud in the mouth of the ASV is minimal.
The ASV control mechanism is deleted and blocked open.
That injector nipple is normally capped with a rubber plug.
The ECM not being 'seen' by VCDS could be a problem or just a one-time fluke.

flee said:

EGR solenoid will vent to the airbox when the valve is 'off'.
The amount of crud in the mouth of the ASV is minimal.
The ASV control mechanism is deleted and blocked open.
That injector nipple is normally capped with a rubber plug.
The ECM not being 'seen' by VCDS could be a problem or just a one-time fluke.

Click to expand...

Thanks for the reply.
Seems like there are more mysteries unfolding. As is the life of buying a used car 'as is'. I enjoy figuring out the puzzle though.

So, to confirm, you're saying someone has modified my ASV?
That bit of JB weld, or caulk, or whatever used to plug that hole looks suspicious, but I Googled pictures of a TDI ASV, and (best I could tell) they all have that opening blocked off.
Additionally, I have toyed with the lever/rod actuator mechanism, and the valve opens and closes.
Why would anyone delete the ASV but not the EGR? From what I've read the EGR is usually deleted first, and only sometimes is the ASV additionally deleted.

The "no communication" code is recurring.

Sorry, it looked like the linkage was missing. It's just the angle of the photo.
Some people have blocked their ASV open when it failed and shut off the engine.
Try to determine why the ECM is having trouble communicating with the VCDS.
Stuff like corrosion, wire damage, low voltage, etc.

Finally got my new vacuum hose in the mail from IdParts.
Good stuff.

Replaced all the hoses. Got a good bit of power back, but not all of it...
I can now responsibly maintain 70mph on the freeway, and even technically catch some speeding tickets, but the motor still falls on its face under throttle.

It acts okay down low, starting from a stop, but struggles past 2000rpm.
Unplugged MAF, definitely got some power back, but it can be a bit difficult to tell as the car drives differently when going off preset fuel tables.

Even though I was hoping for more conclusive data (prior to vacuum
Hose replacement) that the MAF was certainly bad (as opposed to an air leak somewhere else pointing fingers at the MAF), I ordered a new one a few days ago. Glad I did as it should be here Monday.

About the MAF data - I did have readings from VCDS. Actual vs theoretical MAF readings would vary wildly. The thing though was that the theoretical MAF values weren’t quite right either. Oh well, doesn’t matter now I guess.

My new MAF (Bosch brand off an eBay listing - will post link later. The link was provided in a thread on this forum about a week ago. Bosch MAF for $40 shipped)

I got all excited to replace the MAF. I was a bit uncertain as the MAF seems to be “intermittently” bad. Sometimes if I stab the throttle at certain speeds, it will ‘catch’ and give the sweet booooost juice. Other times, it surges and struggles for power.
Literally will surge up and down with the throttle pedal pinned to the floor. Will surge up to 2600 rpm, fall to 2000, surge to 2500, fall to 2000, etc.
constant/smooth vehicle speed though. No bucking or jerking.

I checked the MAF graphs on VCDS. They reflected my butt dyno findings - Actual MAF readings sometimes reflect requested readings under sudden hard throttle, but quickly diverges under gentle throttle.

Before I made the new MAF un-returnable (installing it) I was considering posting a thread along the lines of “intermittent tell tale signs of failed MAF - still blame MAF?” But I thought replacing the MAF was a no brainer.

Well, I got the new one in the mail. Went to swap it out. The old MAF looked identical but it looked like an eBay knock off - no branding or markings at all. Hmmm...interesting.
Put the new MAF...absolutely zero change or improvements.

Guess I’ll make a dedicated thread for that and start looking into turbo components.

You do know you are dealing with an 18-year-old car with a terrible automatic transmission............could be many other things worn out other than the MAF.

You have gone through a bunch of stuff so far in trying to diagnose what is really going on. You mention the MAF requested vs. actual if I read correctly, and it was inconclusive. In my experience if you stab the throttle and it sputters but if you back off the throttle and ease into it and you get power there is a definite tracking issue on the turbo actuator. There are many different things to check: can you check the vacuum on the actuator when you are at full chat? Have you checked from left to right (drivers side to passenger side) the amount of vacuum at each solenoid? You may have a cracked solenoid and you are not maintaining vacuum across the board. If you have 24" at the vacuum pump--or close--you should have the same amount of vacuum all the way to the ASV on the passenger side of the engine bay. I went through this same issue once upon a time, and even though it was years ago, I remember it like it was last week.

Nevada_TDI said:

if you stab the throttle and it sputters but if you back off the throttle and ease into it and you get power

Click to expand...

my situation is the complete opposite.
When I stab the pedal, I get a jolt of power - and the MAF readings reflect this - but if I ease into the throttle, the MAF diverges further away.
I got some screenshots of the data graphing off VCDS.
This one shows that the MAF is quite responsive under quick stabs of the throttle. This experience gave a good bit of boost, and the car pulled well.

This shows, again, the MAF responds to a quick stab, but falls away to a low value if I keep the pedal floored. The green line (MAF requested) is 100% synonymous with how hard I'm pressing the pedal, while the yellow line is the actual MAF readings. Red is RPM (which slowly rises) and the blue is EGR valve.
I kept the pedal floored for 30+ seconds here. Barely maintained 30mph on flat ground.

This graph shows, again, the MAF responds repeatedly and reliably to pedal stabs, but quickly falls away.

This graph is just me stomping on it repeatedly trying to find the "boost on" condition. The yellow line spikes a few times here, showing the MAF is actually capable of reporting ~700 mg/str

By the way, I replaced the vacuum lines 2 days ago. Drove it, felt like I got some power back.

All (if any, lol) power I "got" back is pretty much gone now. What a mystery...