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AWX 1.9tdi no boost following cam belt change

janome Sep 23, 2013

  1. janome

    janome New Member


    the bolt that holds the cam belt idle pulley sheared on my 02 A4 last week, 2k miles before the belt was due at 180k! I have had the cylinder head repaired and refitted with all new parts, I also had to have a new bottom pulley as the idle pulley trashed it when the bolt sheared and a new oil pump cover plate which also cracked in the excitement. The engine is back together and idles fine but it has no apparent boost as the torque has disappeared. I have checked all the obvious, hoses etc and replaced the vac hose that goes to the intercooler pipe on top of the engine with no improvement. However I have noticed the following:

    1. The fuel temp sensor has one of 2 wires with worn insulation and you can see the copper strands have mostly parted ( I disconnected this sensor but it made no difference). Does it matter
    2. The fuel lines from the filter that run across the bulkhead and to the pump unit(?) by the offside shock mount and back are really hot to touch (too hot to hold onto). Does this mean that the fuel pump is spilling all the fuel back to the tank?
    3. The vac hose in point 1 has a small black and white non return valve in it, which way should it face?
    4. The engine is very slow to accelerate when revved in neutral.
    5. There is a faint judder in 1st and 2nd when accelerating
    6. My normal mpg has dropped from 50 indicated to 38 for the same 85 mile trip to work.
    7. The aircon which has been re-charged will not work, the econ light stays on when you press it. I mention this as the only time I have ever had engine shudder before was when the aircon was overcharged.
    I changed the MAP sensor on advice but was not convinced as it was fine before the belt failed, again to no avail.

    Anyway, the garage that did the work and I are scratching our heads as to possible faults. Any advice appreciated please
  2. Chillout

    Chillout Active Member


    Sounds like you need a scan done the check valve should point towards the engine as it pulls the vacuum you should be able to suck through it but not blow .
  3. janome

    janome New Member

    Thanks for the check valve tip I will check it out and let you know.
  4. AudiLeon

    AudiLeon Well-Known Member VCDS Map User

    How are the brakes? Check again the vacuum lines running from the vacuum pump at the rear of the engine. The pump can be an ****.
    Has the head been skimmed? I've seen stories where 1.9 PD engines with skimmed heads lose power.

    Have you run VCDS on the engine?
  5. janome

    janome New Member


    the brakes are fine with plenty of servo assistance. I have ordered a new check valve as previously advised (£12+vat from TPS) and reversed mine in the meantime, and it has restored some boost. However my existing check valve itself is damaged (from being in backwards I think) and it now passes both ways with only a little bit of resistance in the non return direction when it should be a complete dead end. I only hope that none of the other pneumatic actuators have been damaged and that this is the problem. Found a few threads on other forums about this check valve. I will let you know tomorrow, if the check valve change works I will not get a code read, otherwise it is back to the garage. Unfortuantely I do not have vcds and yes the head was skimmed.

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