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Time to perform a diesel purge? - Injection Quantity Deviation

Discussion in 'VCDS (formerly VAG-COM) forum' started by Lund, Aug 3, 2012.

  1. Lund
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    Lund Member

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    Hi all,

    Been exploring VCDS with my ross-tech cable and had a look at the injection quantity deviation. It produced the following results. From my understanding above or below 0.5 is not 100%? I understand the engine will change injection quantities for a smooth idle, but cyl.3 & 4 appear to be slightly off!

    [​IMG]

    Any other checks I should be performing whilst I'm at it?

    Thanks in advance,
    Tom
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  2. NHN
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    NHN Modmetractor

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    I'd be interested to see 1st what you use for the purge & 2 the results, interesting.
    Last edited: Aug 6, 2012
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  3. Lund
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    Lund Member

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    I'll be using some Liqui Moly Diesel Purge and I'll re-do the measuring block afterwards as a comparison. I'm not normally a fan of 'additive culture', but I have read good reports and noticeable improvements. You run this stuff straight.

    Before I go ahead with the purge I'm going to do a quick test of a friends A3 140PD to see how his injection mg/per stroke differs to mine.

    I'll keep you posted.
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  4. NHN
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    NHN Modmetractor

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    I may do this myself after your results :)
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  5. Lund
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    Lund Member

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    Excellent; bare with me whilst I collect the necessary parts (I have ordered the purge). I'm slightly concerned about the temperature the fuel hoses reach and the type of silicone tubing used, although it should be OK.
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  6. NHN
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    NHN Modmetractor

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    Yeah I read most of a 450 post thread on tdi forum lol, some tubes have melted lol, so also concerns me, but just use some used oem pipes, that should be ok.
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  7. max69vk
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    max69vk Active Member

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    Looking at your details above cylinder 4 is well off, all the other units are attempting to balance out. Cylinder 3 looks ok, but its trying harder to balance out no 4.

    If after the purge the figures still look like above then it's either a problem with the injector on that cylinder (unit faulty or injector seals faulty), or as a worse case a worn lobe on the cam - Could also be worth checking you injector clearances as I've been hearing more & more about how its a good idea to check them every 20k miles or so.
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  8. Lund
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    Lund Member

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    Cam lobe wear is particularly rare, its unlikely, but not to be discounted. The car doesn't feel down on power/poor running/low MPG, it all appears fine, so it looks as though it is compensating for the 4th injector well.

    Purchased the Lubri Moli Purge, 5/16 PVC Tube & 6-8mm in-line fuel filter. Just the vacuum piece to be had now, although proving to be difficult to source & expensive for abit of plastic, I'll see what I can find.

    Also, ran a log of the boost & charge pressure, but haven't had chance to explore the figures.
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  9. Lund
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    Lund Member

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    Purge in process! :thumbsup:
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  10. NHN
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    NHN Modmetractor

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    Watching with excitement :)
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  11. Lund
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    Lund Member

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    I have just finished the diesel purge on my A3 2.0TDI 140PD. The following procedure and results are as follows;

    Parts:

    • Lubri Moly diesel purge
    • 1m of 5/16 PVC tubing
    • 6-8mm in-line fuel filter
    • 5/16 plastic Vacuum fitting
    Tools:

    • Stanley knife
    • Quality pliers
    • Glass jar
    • 10mm Socket & ratchet (engine cover removal)
    Plan out where to place the glass jar, in-line fuel filter and measure out a few lengths of PVC tube and cut accordingly using the Stanley knife. Connect the in-line fuel filter to the fuel-in line with the arrow in the direction of flow.

    Use the pliers to pinch the fuel line clips on the engine side (not the fuel filter clips) and remove both the fuel and return line (Give it a twist and abit of persuasion). Connect the two fuel lines using the vacuum fitting and reset the clips.

    Now, connect the PVC line with the fuel filter to the 'in' and the length of PVC tubing to the fuel 'return' pipe. Place the ends of both into the glass jar. You are now ready to fill up the glass jar 3/4 full using the Liqui Moly purge. (I used a few lengths of masking tape to secure the glass jar in place).

    [​IMG]

    Check all connections are sealed and you are now ready to start the engine.

    [​IMG]

    Start the engine and run the engine at different speeds, I did repeats of 1K, 2K, 3K held for a few seconds with an occasional full rev. Continue to top-up the purge to ensure the engine doesn't run dry of fuel. (I used roughly 95% of the bottle of purge).

    Having performed the purge and switched the engine off, the colouration of the remainder of the purge looked like this:

    [​IMG]

    The procedure for removal is the same as fitting, just be careful as the engine and fuel lines will be hot.

    And the results after re-connecting the fuel lines and plugging in VCDS?

    .
    .
    .
    .

    [​IMG]




    :thumbsup:
    Last edited by a moderator: Aug 15, 2014
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  12. NHN
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    NHN Modmetractor

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    This is for sure a brilliant writeup, commend you for this mate.

    So any noticeable results with the car usage now, I see differences in the readings but what about driving.

    Are you going to do an oil change as there has been a fair bit of talk of the purge affecting the oil properties tbh mate, read most of that 450 post thread on TDI & causing more engine wear, so I would suggest a short test drive & then a either oil/filter change/flush or just a straight forward oil/filter change.
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  13. Lund
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    Lund Member

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    Hi Nigel,

    Thanks for your response. I haven't driven the car yet, but will do later on today. You're quite right, I'll be ordering some new oil and an oil filter this weekend as it has been 5000miles since my last filters and oil service.

    You might have noticed from the video, what I do need to do is replace the alternator pulley as the 'clutch' has seized causing the aux tensioner to work harder!
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  14. PAULF
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    PAULF Active Member

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    Well done!

    That's some interesting info there, backed up by figures.

    Like Nigel, I would be interested in knowing if you feel any difference - or get any MPG improvement.

    I'm never sure with this sort of thing if there is actually any improvement, or if it's just wishful thinking. Those readings clearly show an improvement.
    I might have a go on my V6s and see what it does.
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  15. Lund
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    Lund Member

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    Hi, I'm reporting no noticeable difference in driveability or in MPG, however the engine does sound quieter and if anything less agricultural! It has done some good.
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  16. jimpa10
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    Surely you have improvement,i made similar thing in my citroen( by a specialist not from me) but all of them went to -0.20 - 0.25 .i want also to do that in my a3 with your method but i saw that 1 cylinder mesaurements changed slightly up.
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  17. Lund
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    Lund Member

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    Hi Jimpa10, Nothing all that noticeable - I once had my distributor on my '79 mini 180deg's out, it was like this for months. It was pointed out to me, I flipped it around the correct way & sure enough no noticeable difference!

    The cyl quantities all change all the time, I did the purge because cyl.4 was excessive, but cyl.3 was compensating for this. That's presumably why there's no noticeable difference, its just that all injectors are all now working as they should.
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  18. jimpa10
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    i will try next 2 weeks and will post the results.
    thx for the reply
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  19. NHN
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    NHN Modmetractor

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    Yeah I saw the tensioner going mental which isnt right, so I'd do that asap mate aswell as oil as any time used to degrade the oil can have fairly substantial effects even on low usage of miles.

    For me the main thing would be to clean injectors up & get an even spread as such, noise also is a major for me, increase in power/mpg is bonus but not essential.
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  20. Lund
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    That's a brand new aux tensioner and belt, its definitely the alternator pulley, its the clutch thats seized. Where do you suggest purchasing one from? Eurocarparts don't do them unfortunately.
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  21. NHN
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    NHN Modmetractor

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    I meant fix it asap, meaning clutch if this is the case as its putting a vast amount of stress on that belt & tensioner, audi would be my 1st stop tbh mate if they do a seperate part.
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  22. Lund
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    I'll give Peter in parts a call now, thanks.
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  23. NHN
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    NHN Modmetractor

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    So any updates on the injection readings fella & what volume/size purge did you use as I see a 500ml version.
    Last edited: Jan 26, 2013
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  24. bigal23
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    bigal23 Member

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    Any updates? Very interested in this
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  25. niallh
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    niallh Member

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    Ive purchased some fuel lines and the diesel purge, hopefully will be with me by the end of the week so shall be posting my results in the thread
    #25
  26. NHN
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    Well did mine, certainly cleaned out something as came out nice & black, used most of a litre tbh, but went well, coupled with a cam belt, aux belt, tensioners, water pump & rad change, car seems allot better, which is a combo of things overall, but thanks to Tom for the thread.

    Fuel filter will be changed shortly & may do another shorter purge to be sure with new fuel filter in place aswell.
    #26
  27. SAiLO
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    SAiLO Enthusiast

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    Interesting read!
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  28. tecas
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    tecas New Member

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    Hi all,

    What an interesting read, thanks to the OP. I plan on doing this as my engine revs are fluctuating wildly when the engine is cold, looks like the cylinder 3 injector could at least do with a clean-up!

    I was wondering whether anyone has done the diesel purge on a 1.6 CR Engine? I actually have a Golf MK6 1.6TDI which shares it's engine with the equivalent Audi A3. I took the engine cover off and it and the lines are a little more complex coming out of the filter and I am not so sure at what point in the lines I tap into.

    See the reason why I am pointing to injector clean-up needed below...

    [​IMG]


    Thanks.
    #28

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