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Advice on electrical gremlins

Discussion in 'A3/S3 Forum (8L Chassis)' started by Scullies, Sep 4, 2013.

  1. Scullies

    Scullies Well-Known Member

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    So I am still having some misfire issues with the new engine.

    When I start the car from cold, it runs and idles as it should. All 4 cylinders firing. If I tap the throttle a few times the engine revs as it should but then it only runs on 3 cylinders when it returns to idle. It's always misfires on cylinder #3 when this happens.
    Then when the engine is hot the misfire goes away on its own. I don't touch anything, it fixes itself.
    When I am driving the car and its hot there is no misfire at all.

    These are the things I have done to troubleshoot.

    swapped coil packs around - still same issue, misfire cyl 3
    swapped injectors around - still same issue, misfire cyl 3

    I bet you all saying its the coil pack harness now, well I pull the plug off the cyl 3 coil pack, removed the coil pack and stuck a spare spark plug in the coil pack and connected the plug, it was firing away with a nice blue spark.

    So I then check the plug, it was also firing.

    I then decided to reduce the plug gap a bit as they were set to 0.8, I set them at 0.65. The car started and ran fine, so I thought I had found the issue. So this morning I come to start the car, and it runs even worse. Like only 2 cylinders firing, then dies and won't start again, smells like its flooding.

    I then think maybe then big injectors are over fuelling. So I put the stock S3 injectors in and flash the stock S3 map. Unplugged the maf as its in a rs4 housing (thought scaling would be out)
    Start the engine, it start but same as before, runs rough, dies and won't start again.

    other things I have tried.
    changed ecus - no difference
    held injectors into a bottle to see if there are spraying - all ok
    changed sparked plugs - no difference
    changed fsi coil packs with new 1.8t coil packs - no difference.
    Checked coil pack harness for continuity - only check as far up the harness as I could get to without removing the harness.

    things I haven't checked yet, and plan to do.
    check continuity from coil packs connectors to ecu connector - NEED TO FIND A ECU PIN OUT DIAGRAM.
    check engine compression - dont see how the engine runs fine when its hot for there to be a compression issue.


    I await solutions :)
     
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  3. <tuffty/>

    <tuffty/> Badger 5 Edition...Its all about the flow...
    Staff Member Moderator Audi S3

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    What plugs are you using and is the coil pack loom earth connected properly on the cam cover?

    I have an AMK ecu diag... it is also available on google docs if you search for 'vag documents'... PM me and I'll sort you a link..

    <tuffty/>
     
  4. Scullies

    Scullies Well-Known Member

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    This seems to be a suitable ecu pin out list. I hope so :)

    image.jpg image.jpg
     
  5. Scullies

    Scullies Well-Known Member

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    using NGK iridium plugs, can't remember the number though, will need to confirm.
    Yes, harness is earthed to the cover and contact point is clean.
     
  6. <tuffty/>

    <tuffty/> Badger 5 Edition...Its all about the flow...
    Staff Member Moderator Audi S3

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    If they are 8's then have seen issues on cold start with these... try a std set of 6's to see if this fixes it... if it helps then just bung 7's in...

    Also worth trying an earth direct from the battery to the cam cover... jump lead can suffice as a test...

    Are your injectors scaled yet in the map?

    <tuffty/>
     
  7. Scullies

    Scullies Well-Known Member

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    The plugs are definitely 6's, both sets. I remember seeng that.

    will try giving the coil pack harness a direct earth cable - thanks.

    I'm sure the big injectors are scaled as when it runs on all 4 the lambda control is good, but Bill would have to confirm that as I know nothing about that stuff.

    Also it had the same issues with stock injectors and stock map, when I tested that this morning.
     
  8. <tuffty/>

    <tuffty/> Badger 5 Edition...Its all about the flow...
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    What other stuff have you changed since the rebuild?

    <tuffty/>
     
  9. <tuffty/>

    <tuffty/> Badger 5 Edition...Its all about the flow...
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    ...sounds like a cold start/running rich kinda thing... what are the fuel trims doing once warm?

    <tuffty/>
     
  10. Scullies

    Scullies Well-Known Member

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    On the engine, 830cc injectors, rs4 maf housing, stroker engine, cat cams
    bosch 044 setup was running on the stock engine,

    On stock injectors, stock ecu file and stock MAF in S3 housing.
    Lambda is jumping between 5% and -6%
    Lambda factor is hanging around 1.000
    ltft is 0.2%


    On stock setup the misfire is still happening at startup when engine is "cool"
     
  11. Westy

    Westy Well-Known Member

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    Any other fault codes? Issues with the cam position sensor and VVT sensor can cause misfires. I saw misfires and VVT errors when my alternator was on its was out and I'm guessing the electrical system just didn't have enough juice. Not seen the problem now I have a new power plant.
     
  12. Scullies

    Scullies Well-Known Member

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    Only fault codes I have are,
    N75 unplugged
    evap - incorrect flow ( this is because its all removed except the solenoid thing )

    Alternator is charging the system at 13.5 volts as per VCDS.


    I was wondering it the coolant temp sensor could cause this kind of issue. I vaguely remember that it can cause some weird unrelated faults on the 1.8t engines.


    FYI - engine specs
    Stroker 2008cc - 9.5:1 compression ratio.
    AEB head
    Supertech valve train
    Cat Cams - billet 3658's
    Xcessive plenum/Aeb runners
    830cc injectors
    RS4 MAF housing
    Precision 6262 hair dryer


    Been driving the car around this evening with the stock S3 injectors, MAF housing and sensor and stock 210hp map.
    Usual rough idle at start up, then smoothed out when engine is hot. Drove about 15km into town, engine ran perfectly. Stopped for coffee with some mates for about 2 hours, started car and rough idle for a few minutes, then drove another 15km back home. The engine doesnt skip a beat when its hot and lambda stays very close to 1.00 while on throttle and running on actuator pressure.

    I am still completely baffled with this situation, will see how things are in the morning when I start it up as a cold engine. Think I will change the coolant sensor first as there is no harm in trying that.
     
  13. s3dave

    s3dave TFSI Hybrid
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    Sounds like an earthing problem to me as things expand when hot so propper contact is made? for what it is the CTS might as well be changed...
     
  14. <tuffty/>

    <tuffty/> Badger 5 Edition...Its all about the flow...
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    Have you got 'a n other' AFR gauge/wideband hooked up?

    Sounds like its not liking the mixture on cold start... could be the cams coming into play a bit here too (I don't know the spec)... combo of cams and rich cold start mixture...

    One thing to try if you are up against a wall is maybe std cams...

    <tuffty/>
     
  15. Scullies

    Scullies Well-Known Member

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    Got an extra earth wire from the coilpack harness earth point to the battery negative.
    Strange thing is when its running on 3 cylinders, I can pull the misfiring coil pack out and fit a spark plug to it and it sparks away in the open air.

    Yes, have an innovate AFR with is showing same lambda as VCDS.

    Was thinking this too but dont understand why its only and always cylinder 3 not igniting. Surely it would be across the cylinders :shrug:
     
  16. Scullies

    Scullies Well-Known Member

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    Change the CTS this morning and it make do difference with a cold start up.

    So my thinking it has to be either the fueling or timing at cold start. Must be an issue with the cams as they are rather aggressive numbers. Even when the car is hot and idling right the cams are lumpy and I love that feeling and sound :)

    So was wondering if anyone has used unisettings software or lemmiwinks software to adjust ecu parameters?
    My plan is to try change the cold start up fueling and see how things go.
     
  17. <tuffty/>

    <tuffty/> Badger 5 Edition...Its all about the flow...
    Staff Member Moderator Audi S3

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    Have used unisettings in the past but not on cold start... worth a punt... don't forget to cycle the ignition... and it may take a while as each time you start the engine to test it of course gets warmer... cold start mapping is a ball ache lol...

    <tuffty/>
     
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  18. Scullies

    Scullies Well-Known Member

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    good thing its not cold here :lmfao:
     
  19. <tuffty/>

    <tuffty/> Badger 5 Edition...Its all about the flow...
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    Sadly that could work against you lol..

    <tuffty/>
     
  20. Scullies

    Scullies Well-Known Member

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    :crying:
     

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