Altea TDI 140: spluttering, black smoke, disconnecting MAF fixes it. Turbo?

Discussion in 'TDi - SEAT Diesel specific topics' started by Muttley, Mar 12, 2017.

  1. Muttley

    Muttley Catch that diesel!

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    Been away from the forum for a long time. Redundancy, job searching and etc proved to take a lot of time and sap confidence, leaving me not in a good place. Now I have a problem and hope someone here can help.



    Altea TDI 140 Sport, BKD engine, 130K miles. Good service history, no previous engine problems.

    On the way home from the last of several recent visits to the North East from Kent, sorting out my newly-deceased father's estate, house and belongings (another story, maybe later) the car lost power, stuttering and putting out black smoke. Was able to get home (carried on for 100 miles or so) but all is not well.

    Removing connection to MAF cures stuttering and black smoke. Without MAF connected, engine is down on power, struggles to reach 4000 rpm when under way, but is otherwise polite, does not choke following motorists.

    Put it in to local independent VAG specialist. They say the MAF signals are good, but turbo actuator not holding vacuum. Diagnosis is 'turbo problem', but they (quite reasonably) don't rebuild turbos and the VAG fix for this car is 'replace turbo'. Not able to afford > £1K at this point.

    Tried replacing turbo actuator (not a simple task) setting rod length to match the one we took out. Somewhat better response but still stutters and puts out black smoke. Removing MAF connection still has the same effect, stops the black smoke and reduces power output.

    My hope is that someone here recognises the symptoms and ca either cofirm it is a turbo failure of some kind or can identify what else might be at issue. It's confounding me.

    Will also post in Altea section, to try to catch all possible answers. Forgive me for double-posting this once?
     
    #1 Muttley, Mar 12, 2017
    Last edited: Mar 14, 2017
  2. cheshire cat

    cheshire cat Full Member

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    I think I'd be looking at the egr /intake for leakage /clagging up
     
  3. Muttley

    Muttley Catch that diesel!

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    Hiya Chesh. No audible boost pipe leakage. I cleaned the EGR, but that was a couple of years ago. It's just so odd that disconnecting the MAF cures the problem, and I was hoping someone else may have had the same symptoms. I've changed the thread title to make that a bit clearer.
     
    #3 Muttley, Mar 14, 2017
    Last edited: Mar 14, 2017
  4. Muttley

    Muttley Catch that diesel!

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    Update: A second investigation by a local garage/service center/whathaveyou has found a hole in the intercooler. This would fit the symptoms pretty well - when the turbo goes you usually know all about it. So, fingers crossed that that is all it is. Will soon know. No idea how my usual mechanics-of-choice missed this.
     
  5. Dan FR

    Dan FR Meth addict. Stage 2+ Yo!

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    It'll be the intercooler - loosing all of your metered air that the ECU has accounted & fuelled for. Stay away from first mechanic in future
     
  6. cheshire cat

    cheshire cat Full Member

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    great :) old DUMB pressure /boost guages are worth their weight in gold
     
  7. Muttley

    Muttley Catch that diesel!

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    Intercooler replaced and new seals all round. No smoke, no stuttering, boost is back to what I expect. Have hit limp mode a couple of times. I suspect the turbo and maybe the cat are a bit sooty, I will try to get the turbo nice and hot and see if it improves things.
     
  8. cheshire cat

    cheshire cat Full Member

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    great stuff now for an Italian tune up :)
     
  9. Muttley

    Muttley Catch that diesel!

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    Some further remedial work needed, so I took it back to the guys who diagnosed and replaced the intercooler: it turns out that when we replaced the actuator, we set the rod length by counting threads, and did not notice that the rods themselves were of different lengths... Embarrassing error, and it accounts for the overboost in no uncertain terms.

    Rod reset to correct length (by comparing it with the original, which we still had), and a little tuning done to match boost demand to boost delivered.

    My goodness, what a difference. Not only am I now a good citizen, leaving no black sooty trails, the power delivery is better than it was before the work, and the fuel economy is notably better too, on short runs something like 5mpg better. Not done a long run yet, but it all looks very good.

    So, probably two faults, the leaky actuator (which may be due to age, or the strain of dealing with the holed intercooler, or both) and the intercooler itself. What seems to have happened there is that one of the square-section tubes has failed along one edge, which is where they are weakest of course. I suppose that they flex a little when containing boost.

    So all is well again. Except now I have to investigate why the mirrors have stopped working. I suspect the switch, but it's not a simple matter to get the console off so I can have a look at it. And its not just a simple set of contacts, no, there's resistors in there too. Never a dull moment.
     
  10. cheshire cat

    cheshire cat Full Member

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    moral of the tale "Never throw anything away" never know when it "comes in" :)
     

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