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Discussion Starter #1
I have a 2002 TDI Golf with 165,000+ miles on it. Engine light came on last week - unfortunately it happened while my wife was driving, so I didn't have the chance to notice anything going on. Wife did mention a lack of power.

Used the VCDS and got code P1556. Read up on the various forms of limp mode. Checked the MAF and that doesn't seem to be an issue. Checked out the MAP, and I think this is the problem. The actual MAP never reaches or exceeds the specified value. (I would include a graph, but my only windows computer is ridiculously old and doesn't network)

Took it out myself and there's a stutter/flat spot around 1900-2100 rpm in 3rd, 4th, and 5th. Accompanied by some black smoke out the back. Engine light is off, after being cleared.

Checked the vacuum lines with a Mityvac. Not sure how effective this was, but I didn't see/hear/feel any leaks. Swapped EGR for N75 and no issues (except for a fault code for N75 ground).

However, the line into the actuator wasn't holding vacuum. Tried moving on my own, but no luck. Had the wife turn the car on while I looked at the actuator and saw no movement. Tried spraying with PB blaster, but no movement still.

I'm guessing next step is to take off the actuator and try cleaning it out before replacing if need be. I'm wondering if I don't have a clutch issue though, as the stutter around 2000 rpm doesn't happen in neutral, 1st or 2nd.

Any thoughts?
 

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Used the VCDS and got code P1556.
A P1556 error code is

VAG Error Code: 17964

EOBD II Error Code: P1556

Fault Location:
Turbocharger (TC) pressure - control limit not reached

Possible Cause:
Turbocharger (TC) wastegate regulating valve.
Intake leak.
Turbocharger (TC) defective.

As taken from Free EOBD II Error Codes software ;)
 

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Discussion Starter #3
Thanks. I have the Bentley book and can see the code information (in addition to seeing the codes in the limp mode FAQ here).

In the course of working on it today, I've noticed an oil leak which looks like it is probably turbo based too. Am I going to have to buy a new turbo oil feed?

Also, anyone have an suggestions for good places to pick up vacuum lines? I'm thinking of replacing them while I'm working on all this, to make sure I don't have a leak I can't find.
 

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Used the VCDS and got code P1556.
This is normally a boost leak, sticky turbo, sticky actuator, or boost control problem like solenoid, wiring, or vacuum lines.

Took it out myself and there's a stutter/flat spot around 1900-2100 rpm in 3rd, 4th, and 5th. Accompanied by some black smoke out the back. Engine light is off, after being cleared.
Just this symptom is often a boost leak. Do a quick inspection of all the intake piping and look for sooty spray. Then do a pressure test to rule out hidden leaks or leaks that only show up under pressure.

However, the line into the actuator wasn't holding vacuum. Tried moving on my own, but no luck. Had the wife turn the car on while I looked at the actuator and saw no movement. Tried spraying with PB blaster, but no movement still.
This sounds like a bad actuator or vacuum line depending on how far upstream you were testing the vacuum. It should hold vacuum so either the actuator or the line is leaking. Doesn't sound like a clutch issue but this is just an early guess.
 

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Discussion Starter #5
I put the mityvac on the line that goes from the N75 to the actuator. Does it make sense to take the line off the actuator and try to hold vacuum backwards, or will is just lose vacuum going backward through the N75?

Plan of attack will be to take off the actuator tomorrow, figuring I'll either clean it or replace it and either way I need to take it out.
 

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No, since you've found a problem here I suggest using a good line to the actuator. Assuming your vac gauge is good, if it holds vacuum you know the problem is the line. If it doesn't you know the problem is the actuator.
 

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Discussion Starter #7
Having a hell of a time getting the circlip off. I've tried coming from above, below and behind the subframe with a long flat regular screwdriver and a tiny screwdriver (eyeglasses type small). Tried to get in with needlenose pliers, but there are too many things in the way to get a grip?

At this point I would be happy to break it off and get a new one, but even that is proving frustrating.

Any suggestions?
 

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Discussion Starter #8
While working on that stupid clip, here are my observations:

Previously, the VNT lever wasn't moving. Now that I have the two nuts off the actuator, the lever is moving, but it appears that the rod is frozen (can't move it by hand). I'll know more if I get the thing off, but if this is frozen does that mean I need a new turbo instead of just a new VNT?
 

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Discussion Starter #9
Update: After much swearing, the circlip is off and uh, somewhere in or around the car.

Also, the VNT lever (still on the turbo) has full range of movement. The actuator rod is completely seized, though the actuator is holding vacuum. Time to order up a new actuator.

Also found that the adapter from large hose to small hose from the N75 to the actuator was leaking slightly.
 

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Yep, those darn clips like to fly off. If the VNT lever on the turbo moves easily through the full range of movement, it has no problem. Strange how the actuator rod would seize up like that. Any corrosion around the base of the rod?
 

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If the actuator was frozen, wouldn't the vanes just not move? I would think this would cause no shuddering, just constant and major lag. Are you sure it's just not tight? Can you press the rod in? It's not supposed to pull out.
 

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Discussion Starter #12
Major rust all over the base of the rod and the top of the actuator. Not moving even a little bit. Ordered a new one last night. Hopefully get it and put it in by next weekend.
 

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Discussion Starter #13
Put the new actuator in. All the tests read normal and the old one was clearly seized. Put everything back and now I have vacuum from N75 to and with the actuator. Checked the MAP using VCDS and there is a clear difference from before (peaks and response and the actual and specified now follow each other). Everything looked good until the test run.

Took it out and again had shuddering in 3rd and 4th gear around 2000 rpm accompanied by a puff of black smoke. There was no such shuddering around 2000 in neutral, 1st, or 2nd. I only have a stationary computer, so I can't log the details when I'm in 3rd or 4th gear.

Is it possible that there's plenty of residue leftover from the prolonged period when the old actuator was seized? Should I try to drive through it and see if it goes away or is that a recipe for disaster?

Here's hoping I don't have to take the turbo off.
 

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Discussion Starter #14
It just occured to me that I could lift the front tires on jack stands and cycle through the gears while using the VCDS. Not sure if it will help anything though since there will be no load (going up hill or the like), and that could be the issue.
 

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Keep driving it for a while and if it's not fixed you have a clue what is the problem. Be careful when it's on jack stands....you don't want to end up with a Ferris Bueller.
 

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Yep, those darn clips like to fly off. If the VNT lever on the turbo moves easily through the full range of movement, it has no problem. Strange how the actuator rod would seize up like that. Any corrosion around the base of the rod?
Not totally uncommon, mine was frozen solid - even a hammer wouldn't release it. Order an extra circlip with the new actuator, lost my first one when it flew off. Don't trust the adjustment on the frozen actuator, it'll be a good starting point to make the lengths equal off the car, but once on the car, test with vacuum pump since you already have one - mine was somehow either frozen in a wrong position or not adjusted properly to begin with, and when I matched the new actuator to it, I ended up overboosting nicely.

EDIT: oops, just noticed page 2, sorry. Anyway, I wouldn't cycle through the gears on jack stands, thats a scary thought. The only shudders I've had might have been different - more like an engine vibration - and was cured with a treatment of diesel purge.
 

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Discussion Starter #17
More updates:

Drove it about 70 miles today (two 35 mile trips). First trip, belching blake smoke in 2nd, 3rd, 4th, some shudder or power hiccups and audible turbo engage in mid 2000rpms. I was consistently pushing to just over 3000. After the car was good and warm, it seemed to calm down. Power wasn't great at 65mph+ in 4th or 5th, but not unbearable. Smoke stopped in the 2nd half of the trip.

Way home, the black smoke was back and noticeably worse for the first portion (pre-highway) part of the trip. Hiccups or shudder was worse... until the CEL came on, at which point everything seemed to be back to good/normal with no issues (besides the light). Once the light went off, I had no issues with smoke or shudder. Checked the light when I got home and it was again p1556.

Should I be adjusting the actuator? I can't find a decent spec or rule of thumb on the distance there.

Also, when I was putting the new actuator in, realized my intercooler pipe wasn't fully closed and there was oil coming out of it. Thoughts?

I'm driving it to work again (85 miles roundtrip) tomorrow (Monday). Should I be driving it harder to burn the soot off? Do I wait to drive it hard until it is completely warmed up?
 

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Always warm up any car with easy/moderate driving. Adjust the new actuator the same length as the old one but always vacuum test it first using the procedure in the vnt actuator writeup.

A little oil out of the intercooler pipe is normal because the oil mist in the intake system from oil blowby and the crankcase settles at the low spots. A lot is possibly a blown turbo. Perhaps the intercooler pipe blew off again?
 

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sticky vanes

I have a 99 New Beetle TDI that I bought to fix up.
Something destroyed cylinder 1 (no fuel/dry, injector stuck open ? etc)

I've purchased a (sadly a bit high mileage (for a non diesel anyway)) ALH engine
out of a Golf with an automatic (11mm rotor pump !).

Looks like the turbo on that engine, along with a turbo I got with the car both have
stuck vanes... so I'll be going through the procedure.

Hopefully no hidden surprises once work begins.

On a related topic... why couldn't they make the actuator ouf of stainless steel !
My wife's car will be on her 3rd actuator (also a 99 New Beetle TDI) when I finally
get around to replacing it. The first one let go when you could not get one anywhere
(bought a used turbo which blew up (I'm guessing debris got into the oil feed connection ?)
then swapped her old one back on with the actuator from the used one).
 
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