505 STI Cold starting
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  1. #1
    Fellow Frogger!
    Join Date
    Feb 2002
    Location
    Tamworth NSW
    Posts
    496

    505 STI Cold starting

    One of our fleet is a '84 505 STI with the ZDJK engine.

    On initial start from cold, the engine 90% of the time runs on 3 cylinders for several seconds, before "clearing" and smoothing out on 4.

    Since this symptom appeared some time ago, I have checked all vacuum and breather hoses, added hose clips to some, and replaced others.

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    I have replaced the distributor cap, rotor, leads and spark plugs, had the injectors serviced, retightened the cylinder head and adjusted the valves.

    The performance of the engine otherwise cannot be faulted (it has covered 370,000 km). It does not use any oil between 10,000 km oil change intervals. Coolant usage, given that the STI does not have the expansion bottle as fitted to the GTI, is limited to a drop in the level to about 3 cm below the cap level. The excess is dumped overboard with heat expansion.

    The coolant however, has an oily appearance (without discolouration). I have noted this on other STI / GTI models also, but this does not mean it is normal.

    The cold start injector is working normally.

    Could it be attributed to one of the Bosch devices (air or fuel pressure regulation)? Once, when the car stood for 2 weeks during the holidays, it took some 30 seconds to clear the offending cylinder.

    Any thoughts?

    Cheers,
    Kim.

  2. #2
    Fellow Frogger!
    Join Date
    Jun 2001
    Location
    Sydney NSW Australia
    Posts
    137
    Kim,

    Have you undertaken a compression test with the engine cold, after standing say overnight.

    Is it possible that you have a minute coolant weep into one cylinder when the engine is cold? (even though you report minimal coolant loss) - and when engine warms up, the 'gap' is closed.

    Hopefully a compression test would show this up - in which case you would have a warped cylinder head.

    Denis

  3. #3
    Fellow Frogger!
    Join Date
    Feb 2002
    Location
    Tamworth NSW
    Posts
    496
    Denis,
    No, I have not done a cold compression check. It might be useful, so will do when I can.

    As you suggest, the leak must be minute. I have had the system pressure checked via the radiator, and it held a constant pressure. The symptoms have basically not changed over 3 or more years.

    Cheers,
    Kim.

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