tricky power loss problem

im at a loss with my 00 alh, hoping someone can point me in the right direction.
211k on the engine and car
i owned this car for a month and put about 1000 miles on it. i've done a handful of things to it bringing it back from the sad state it was in (list below). but i still get semi random power loss and a interment 17656 code (no other codes), the engine also feels weak past 3600 (could be me). when accelerating hard i lose all power, cant gain any rpm past the point of power loss. it random as it happens anywhere from 2500-3200 rpm. if take my foot of the accelerator pedal then reapply power comes back. logs seem to point to timing control issue

-set pump timing with VCDS just a hair below the blue line. vdcs says its in spec. last owner of this car had been running without the pump timed, engine had no power. timing fixed most of this.
-vag shows timing retard as cold start duty cycle is reduced, correct reponce
-wiring seem to be good for the #3 injector
-check vnt system and turbo due to engine running in a weak state. actuator starts to move at 4psi and is maxed out at 18psi. all is well
-found a miss reading, installed the maf of my 2.0 8v (aeg). maf numbers as on point with requested.
-last owned installed a boost gauge in this car. boost spikes to 20psi and hold steady at 13psi. when i loose power boost holds at 7 psi steady.
-IAT temp stays below 50c under hard long pulls, possible IAT derate?
-ran a full tank of diesel with a high dose of diesel clean though it, little change
-a full service with mann filters was done when i got the car. new fuel, new oil and new air filters were installed
-car has not been run out of fuel in 1000 miles

thinking possible injection pump issue/#3 injector lift sensor issue. but how to trouble shoot?
any help would be nice.

Follow Ross tech for the code. Is it an auto or manual? Any mods done to car?

I would suggest putting a tdi MAF in there. I tried running a 2.0 MAF once upon a time and had nothing but issues with it. Past that your turbo is not culprit. Said code is an internal pump regulation fault. You can check to see if your low pump regulator has fallen apart, make sure your pump return check valve is OK, and try running your pump straight out of a diesel purge can. Hopefully you don't need the pump overhauled just yet.

-no mods (that i know of). i did reinstalled the egr system and verify it was working.
-manual trans/ factory manual car (seems conversions are getting popular?)
-followed the ross tech guide, have a question about what is ment by "Injection Pump Control Range blocked/dirty"

-havn't ran is strait out of a can. i ran some DP though that car when i first got it as a precaution. the car idles fine, drives fine. this problem isnt all the time, i can get on the highway about half the time with out issue shifting at 3400. i been driving it this last month to trouble issues and repair my other mk4 jetta.

i just installed the 2.0 maf because i had it sitting around in my box of mk4 parts, i plan on getting a new maf. i think i have a problem! i own to dark blue 00 jettas and the family owns or had owned a hand full of mk4's.

details on t/s the pump?

Inside the pump there is an electromagnet that controls the position of the quantity adjuster. It's not uncommon for fine metal particles to build up around it, causing the magnetic field to be unstable causing performance issues. That, or it can physically block the adjuster from moving if bad enough.



I've heard that you can modify the 2.0 MAF's to work in the ALH's, never done it myself. You can do some searching on it, give it a try. May work.


As for the pump, there's two things you could try. The easier option, take the fuel supply and return lines off the fuel filter that run from the pump, and put them in a can. Fill said can with Diesel Purge. Run the engine on just that fuel in the can, occasionally revving the engine up to 4800 RPMs. That will shock treat the pump into cleaning it, plus move the quantity adjuster through its full sweep. You only need to hold it at high engine speeds for 5-8 seconds, and only need to do it 2-3 times. After that, just let it idle, until the can is nearly empty. When it is, shut it down. Reconnect the fuel lines as normal. Then let it sit overnight. This will let the Diesel Purge soak in the pump and clean any other crud out. After that, drive it hard, see if there's any change.



If that doesn't work, you could try to take the quantity adjuster off and clean it. I personally wouldn't do it, because it requires very precise soldering to put back together. Next step would be to swap the pump out. It would be cheaper to replace the pump with a known good unit, as overhauls on them are upwards of $600.

okay. so more of less i've done that but no exactly. filled the new filter with diesel purge and ran it. a drove (over a few weeks) a full tank of fuel with a full bottle of diesel clean in it. 12gallons+30oz of power service (silver)

looks like i will get a used 11mm pump (upgrade from what im reading) there $200 local me to me.


i found some tread on my of the tdi forums were a get tested the 2.0 maf and found that is is the same maf just with a built in IAT on pin 5 (tdi only has 1-4 in the maf plug). reading from a TDI maf and a 2.0 maf were the same on his car. still will get a new one. i just find it funny that 18 year old gas maf still worked right when the tdi mafs seem to die as the norm

Nero Morg
can you point me in the direction of some info on how to setup the quantity adjuster? i took the QA apart, found some metal. cleaned it up and carefully reassembled it. per the info i found youtube and online.

the issue im having is the QA sensor will not read above 2.5 volts when a throttle request is being given. it will pas the sweep test both visualy and watching Group 19.
group 19 reading are .620v and 4.3v
group 1 reading at idle is 1.75v

the voltage increases with out jumping or lagging up to 2.5v but it will not go above it. as a result i can not increase rpm past a current point.

If group 019 looks OK, then there may be another issue. What is your injection quantity set at? Mind you, measure it when you're at operating temperature. Are you still getting any fault codes?

OP, I am a bit confused... you had the top off of the IP with the engine running to watch the Quantity Adjuster? Generally speaking after opening up the IP, if the pin does not go into the ring of the QA, the engine will not exceed a certain RPM.

Just watched it sweep with the top off, beyond that monitoring with VCDS.

Could the wires to the coil be sufficiently compressed under the screws to limit hold-current? Good enough for a quick pull-up but not good enough for holding above certain levels? Just a thought, however unlikely.
We know the control shaft can reach the limit, and springs back healthily, I'm wondering if it's in the coil wiring or control.

Nero Morg said:

If group 019 looks OK, then there may be another issue. What is your injection quantity set at? Mind you, measure it when you're at operating temperature. Are you still getting any fault codes?

Click to expand...

sorry for the late reply, the long weekend and the like.
anyways solved this issue with a different QA from a used pump. car is now drive-able.
after all this playing around and watching VAG it seems my original problem is timing based. timing steadly retards with rpm untill it misses and blow white smoke at 4300rpm with the timing holding steady at 6ATDC and n108 at 99.8 duty cycle. n108 goes to 99.8 just off idle and stays there, timing just keeps retarding. i have no fault codes.

i have a used injection pump on the bench now so i did some parts swapping to t/s a case pressure issue.
removed and swapped the relief valve, no change
put a lift pump in line to boost the injection pump, no change
checked the return valve on both injection pumps, the both look the same
seem to be at this point i could have a failed n108 that works electrically but not mechanically
all my reading shows that you have to pull the IP to replace/inspect the n108?
how have guys tested case pressure? the only thing i could find was a spec of 48psi at 1000rpm and 75 psi at 2000rpm.

https://forums.tdiclub.com/showthread.php?t=238872

The bolt on the engine side appears to be an acceptable tap location.
Per whitedog, per DFIS, 10mm pump should be about 115psi at low idle, 175-190 at hi-idle.

Glad you found the issue. I've heard that the return springs for the timing actuator can weaken or break in these pumps causing timing issues at higher rpms, and yea only way to get to it is to pull the pump.

thanks for sticking with me on this. i love when machines and cars degrade in maintenance. often to the point of pealing back layers of failed parts trying to get them back running %100 right.

solved!

cant post a picture. someone at some point removed the n108 and cut the inner oring. looks like they left/missed the o-ring in the pump and cut it in half putting the valve back in....
glad this ordeal is over, last owner really worked this car over taking stabs in the dark. bad fuel lines, bad maf, badly miss timed pump (retarded timing), iq way off from being inside the pump and this cut o-ring.

Here you go.

And yes, it does run much better haha