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Please help me diagnose a 1.9TDI PD

myth Mar 18, 2014

  1. myth

    myth Member

    The engine in question is from an 2002 Audi A4 1.9TDI PD, engine code AWX.

    The problem with this engine started a few months ago, when it started to shake under heavy acceleration in 1000-2000 rpm range. If you would accelerate half the pedal, it would accelerate without any shaking.

    The problem was ignored until it wouldn't start at all if the engine was sitting for a couple of hours. In the morning it would start only with a starting spray or if towed. I then decided it's the tandem pump, so I switched with another one. The problem was solved, but in an attempt to repair the old one, I then switched it back and put on the fuel return line a one way valve that was holding the pressure inside the tandem pump to about 0.5 bar. My conclusion was the the tandem pump was leaking fuel, therefore it would not start.

    The engine was running like this until a few weeks now, when it started shaking at idle so hard, I am worried it could tear the timing belt apart! At about 1200 rpm, the shaking is somewhat dissipated but it's now shuddering even at part throttle until 2000 rpm. If you keep the engine over 2000 rpm, you can easily reach 100 mph!

    Tomorrow am I posting a video for you guys to see the engine shuddering.

    Ok, now here's the list of what was done on the car:
    -timing belt was changed about 1 year ago.
    -DMF was changed 2-3 months ago, before all these problems appeared;
    -all filters and oil was changed due to interval;

    And this is what was done since this problem occured:
    -check the fuel tank for debris/water
    -fuel filter change
    -timing check
    -tandem pump switched
    -compression test: exactly 30 bar on all cylinders!

    I have checked the idle speed smooth running control via vag com and this is what it was showing right after start up
    And this was showing after at least 1 minute of idling

    Could it be the injectors? If yes, which is the main suspect? I'm literally running out of ideas.

    Thanks for patience reading this. I really need your help guys!
  2. jojo

    jojo Looking for Boost! Staff Member Moderator Team Daytona Audi S3 quattro Audi A6 Audi Avant Owner Group

    Can't help you out bud, but these engines are usually bullet proof, my 2000 Passat 1.9PD is on 211k miles, original engine, turbo and clutch! Hope it's a cheap fix, those PD injectors aren't cheap!
  3. desertstorm

    desertstorm Moderator Staff Member Moderator VCDS Map User quattro Audi A4 Audi Avant Owner Group TDi

    I don't understand why you ignored a potentially serious fault in the first place that could have caused a lot more damage to the engine.
    And then you change the tandem pump and decide to put the old one back and codge it to try and get it working with the old tandem pump. If you strip a tandem pump you should rebuild with new gaskets / seals otherwise they will leak.

    Have you checked the fuel tank pump is working correctly and the flow is good. Try disconnecting the fuel line from the filter and you can use vag-com on the output tests to turn the pump on, The tank pump should flow 3-4 litres per minute .

    2005 BEW PD lift pump operation and internals - TDIClub Forums

    The in tank pump primes the tandem pump and it is possible that restricted flow is what is casuing your issues.
    If that pans out all OK then :-

    The injector balance is all over the place and that could be due to several things. The cheapest would be the injector harness in the head,
    These don't always give any VAG-COM faults until it's gets really bad,

    GENUINE Volkswagen VW PD Injector Wiring Loom / Harness 038971600 TDi | eBay

    An injector could be faulty, they are usually very reliable but they do fail every now and then. There is a correct process to follow changing these over and I would recommend changing the seals and at least the one pinch bolt that secures the injector itself.
    Strictly speaking all the bolts under the rocker cover are stretch items and should be replaced if removed.
    The cam shaft could be worn a common problem if the wrong oil is used .

    Camshaft lobe wear inspection and replacement on TDI PD engine | VW TDI forum, Audi, Porsche, and Chevy Cruze diesel forum

  4. Wallm0nkey

    Wallm0nkey Member

    If you can log the injector values not the same issue but years ago I was having a problem with a PD engine if it went over
    2k revs when it wasn't fully upto temp. It would shake and splutter throwing out smoke but once it was warm no problem two injectors had lower values the best part of £300 each at the time! Not the same symptoms but worth trying to rule it out.
  5. myth

    myth Member

    Thank you guys for your replies.

    @Karl, I admit I stripped the old pump to pieces and could not find any damage whatsoever and I put it together with old seals but it doesn't leak. Looks like the return valve was an easy fix.

    I haven't checked the flow rate from the tank pump, but when I changed the fuel filter, I connected just the feed line to the fuel filter and put the ignition to fill it up with diesel and I could not hold back the pressure with my finger on the return line. Having that much pressure, should be enough. This was a few weeks ago. Yesterday I put a pressure gauge on the tandem pump to check the pressure. I had 1.5 bar at idle and 3.5 bar at 1500rpm.

    I have checked the camshaft for wear. I was looking especially for worn sign like in this picture http://www.myturbodiesel.com/images/misc/cam/cam7a.jpg but I couldn't find any. I also jacked up the car, put it in 5th gear and turn the wheel to check all the lobes.

    I also tried swapping the injectors between them. I have swapped #1 with #3 and #2 with #4. I hooked up vag com and checked the new values at idle. #1 cylinder now has positive value like it was before on #3. Now the #3 has negative value like it was before on #1. So it must be the injectors, right? This way I ruled out the wiring loom. If it was a problem with the wiring, the values should have stayed there, regardless of the injectors order.

    I also found out the 3 of the injectors are from 2002 and one of them is from 2001.

    By the end of the week I must have a solution to this problem. I have found a crashed passat nearby with running engine and it's ready for scrapping. I will swap from that engine piece by piece until this engine is running as it should. I will keep you updated.

    Thanks again for supporting me!
  6. desertstorm

    desertstorm Moderator Staff Member Moderator VCDS Map User quattro Audi A4 Audi Avant Owner Group TDi

    I would start with the injectors then first as it appears that is what your issues may be.Also the fact that the injectors have different date codes on them seems to indicate they have previously been changed or messed with.
    I did a how to on changing injectors on the UK Passats site. If I was you I wouldn't reuse the injector pinch bolts. They need to be tightened up to the correct torque, too loose and if the injector comes loose it will allow it to move around and it will wreck the head, too tight and it will snap, then you will have issues too.

    UKpassats.co.uk • Login


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