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Mystifying Seat Ibiza MK4 1.2 misfire [SOLVED]

Discussion in 'Ibiza Mk4' started by Aokuan, Aug 19, 2017.

  1. Aokuan

    Aokuan New Member

    Aug 19, 2017
    Likes Received:
    The engine code is BXV.
  2. Aokuan

    Aokuan New Member

    Aug 19, 2017
    Likes Received:
    I have finally solved the issue with the vehicle, so anyone who encounters this issue the following may be of use:

    After doing all of the usual checks:

    Checked Coil Pack - OK
    Changed Spark plug - OK
    Changed fuel injector - OK (Here was the issue I will discuss)
    Compression test - all cylinders on equal PSI (150psi)
    Checked fuel injector wires for correct voltage.
    Checked coil pack wires for correct voltage.

    Work carried out that did not fix the issue:

    Cylinder head- All new valves, new valve guides, valve seals.
    Cylinder head was lightly skimmed.
    New Cylinder head gasket.
    3 New coil packs BOSCH OEM.
    3 New spark plugs.
    New Timing Chain, Timing Chain Tensioner & Guide Rails.
    Engine was properly timed with VW timing Tools.
    ECU was sent off and Tested by ECUTesting.com which was working correctly.

    With all of the work above I was not able to fix the problem, thankfully after doing some research I figured it must be an issue with the fuel delivery.


    I had already attempted a check on the fuel injectors from one of the very first checks, however the fault code would not move when I changed the injector from the cylinder which was receiving the fault code (Expected result was the misfire code would move to a different cylinder after moving the suspect injector). I later discovered that it was all 3 cylinders that had the issue, I'm not sure if it was because of the incorrect delivery of fuel into the intake manifold before the valve which was getting into the other 2 cylinders causing trouble for the ECU firing.
    This was one of the worst problems since the misfiring was evident through the entire RPM range, but only at 3000rpms would the ECU detect a very high amount of hydrocarbons and shut down one of the injectors. This is where the problem was undetectable for me as the computer would shut down a cylinder with the injector that wasn't the suspect injector, which I believe was due un-burnt fuel in the intake manifold being delivered to the other cylinders causing a rich air/fuel mixture then leading them to misfire.


    I purchased a used set of injectors including the rail with it from someone breaking an 52 plate ibiza (with the confirmation that the donor injectors were working correctly - the car that they had come off had the piston break off and hit cylinder head :() , installed this unit on the engine, after starting the car up for the first time it was clearly running a lot smoother. And after some good old italian tune up on the motorway to clear the build up of carbon in the engine. This carbon build up from 5+ months of poor running and misfiring. The engine is now running smoothly, efficiently with no engine management light and now looks similar to a 4 cylinder in terms of vibration :)


    After experiencing this extremely frustrating and mystifying problem for 5 months now this is the cost comparison.

    £500+ in attempt to fix the issue.
    £35 to fix the issue by purchasing a used properly working set of injectors. [:@]

    Ironically enough I took it to an "Auto Electrician" who I trusted and questioned, could it be the injectors causing the fault, after performing all of the checks which would correspond to a perfectly running engine. He replied "The fuel injectors wouldn't cause a fault like this" after knowing :censored::censored: about the checks I've already performed. "Specialist Mechanics" my :censored:. Sadly a lot of mechanics are out there to rip you off and genuinely act nice whilst not knowing their stuff, going off common errors such as the coil pack problem.

    Anyway before performing all of the work and going through the stress that I have in attempt to fix this problem your best bet is to check the exhaust emissions for hydrocarbons and disconnect the suspect injector to see if the hydrocarbons drop, this will tell you if there is a problem with injector spray pattern or fuel delivery.

    Best of luck with solving the issue :) I hope this can save people a lot of time and money!

    #22 Aokuan, Jan 23, 2018
    Last edited: Jan 23, 2018
  3. RUM4MO

    RUM4MO Senior Member

    Jun 4, 2008
    Likes Received:
    That is good news, though as you have now discovered, you can not always rely on experienced experts to help with every problem, even though they usually aske for plenty money which makes you hope that they are well trained and at the top of their game!

    I think that this is what drives so many of us to either dig deep ourselves, or move that car on to some other person.

    Maybe to raise other's awareness of what can happen, I was at my local Audi main dealer yesterday to get my car MOT'd, the customer at the next table in the customer holding area was getting quite annoyed, it did sound like he handed his car in for an MOT and a repair that did not impact the outcome of the MOT test, it sounded like that Audi dealer gave that car what they call a "free health check" - then spent the rest of the day diagnosing and fixing small not MOT related faults, so by the end of the day the MOT was not carried out and the requirements of the initial requested repair were not addressed, that left that car in the workshop over the weekend and all of Monday until after the MOT, any required parts for the repair were ordered up, so that meant no car again on Tuesday with a promise that they would fast track it through the workshop on Wednesday! I must say that I felt that that incident could and should have been handled a lot better and a lot quicker, typical dealer ship service department, upselling and prioritising that over any thing else. After all, customers do not need their cars, do they, dealer just wants your wallet.

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