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Ignition problem?????

Discussion in 'A4/S4 forum(B5 Chassis)' started by matt-e-g2010, Aug 10, 2010.

  1. matt-e-g2010
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    matt-e-g2010 New Member

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    [Aug 10, 2010]
    My Audi A4 1.6 started missing at idle and was sluggish to pull away so put new plugs and it seemed to sort it out, it was getting dark and i noticed it was arcing from the ht lead by the top of plug onto engine, spark was dim but every time engine missed it was a bright spark and engine tone changed, i changed ht leads, no effect on arcing so i thought electricity passes route of least resistance so closed gap on plug, it worked no more arcing, engine was 90% better no missing but doesnt pick up on the throttle as it should,( once at 2000 rpm everything is normal) checked the spark plug and seemed a little burnt (number 3 cylinder) I have fitted a new coil and still hesitant but missing has stopped at idle but misses on acceleration, opened the gap agin on plugs but am going to put new ones in tomorrow.
    Is there anything else that can cause the hesitation, it happens when its hot or cold, im pretty sure its not the maf because no difference when i unplug it, ive also had vag-com and no codes were showing, only the central locking pump, possible leak so totally unrelated.
    Ive changed plugs, leads and coil and engine is still not right, any ideas? The only thing i can think of is fuel but the exaust smell rich and emmisions are higher, but no smoke although there is more steam than usual and water from tailpipe, no smell of antifreeze though.

    P.s for those who may have read my previous Thread, i didnt buy the Other Audi in the end as the clutch was slipping aswel so didnt want to get involved with to much work.
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  3. aragorn
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    aragorn "Stick a V8 in it!" Staff Member Moderator VCDS Map User

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    [Aug 10, 2010]
    perhaps a faulty coolant sensor or lambda probe causing it to run rich? that would make it a bit unresponsive?

    Arcing from a lead shouldnt be happening, did you buy decent leads or cheap **** ones?

    Return the dodgy leads, and get some branded ones like Bosch or similar.
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  4. matt-e-g2010
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    matt-e-g2010 New Member

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    [Aug 10, 2010]
    Its not a bit unresponsive, its a lot, leads are bosch and were expensive, i changed the coil as the terminal on c (cylinder3) was discoulered, my temp guage wasnt working so fiddled about with wires and is working, is that the one you mean or the one on the bottom of expanshion tank?
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  5. matt-e-g2010
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    matt-e-g2010 New Member

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    [Aug 10, 2010]
    Forgot to mention its all on cylinde 3, and checked codes after i changed coil so battery disconnected for hour or 2, would this clear codes and why im not getting any?
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  6. matt-e-g2010
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    matt-e-g2010 New Member

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    [Aug 11, 2010]
    I know whats wrong, its a sticky exhaust valve, will explain the dry fouling in number 3, tested by the good old fashion way of holding a peice of paper by the exhaust, didnt suck in all the time, just evry time it juddered, should keep me busy for a day a head rebuild, do you think im sick in the head as im looking forward to it:)
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  7. murran
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    murran Active Member

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    [Aug 11, 2010]
    compression test? cylinder leakage test? these should show up any scruffy valve seats causing misfire problems.
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  8. matt-e-g2010
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    matt-e-g2010 New Member

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    [Aug 11, 2010]
    Compression was ok as its just starting, and to be honest when a engine is just cranking on the starter its not at anywhere near the stress it is at when its firing. its not missing every cycle, it varies, been through ignition, fuel etc and dont really want to pay for a leak down test to just confirm what the bit of paper told me i.e every few cycles air is being drawn back into exhaust on induction stroke in number 3, im sure its number 3 as thats where the dry fouling on plug is, i will be pulling all valves cleaning and re seating and replace if necisarry, fitting all new valve guides, needed a new cambelt and i wont have to worry about head gasket for a while.
    Last edited: Aug 11, 2010
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