Merc W203 200K misfire forever
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    Angry Merc W203 200K misfire forever

    Merc W203 200K misfire forever
    Car come in with "misfire" at idle. It can misfire ligthly for minutes then run ok.

    Spark plug ok, decided to buy 4 coils. Test car ok. Give the car to customer.

    Car come in with "misfire" at idle. It can misfire ligthly for minutes then run ok.

    Decided to buy 4 injectors. Test car ok. Give the car to customer.

    Car come in with "misfire" at idle. It can misfire ligthly for minutes then run ok.

    Decided to test the timing of the engine, result the engine has correct sync.
    Tested the wiring from ecu to injectors: found one wire of cyl 2 that has an high resistance
    value. Put a new wire from ecu to injector 2.
    Tested compression: cyl 2 has 2 bar less than the other cylinders.
    Send the head to the rework center.
    Head arrived with valve seat rework, valve guide, etc., also 1 new camshaft variator
    New head gasket of course.

    Test the car on street...guess what...between idle and 1500 RPM the engine collect
    now and then "misfire" on cyl 2.

    The engine run fine over 1500 RPM, the number of misfire on cyl 2 does not increase.
    Leave the engine at idle, the number of misfire will increase.

    Suspect of ECU but no one near there want to open this ECU.

    We are litteraly tired of this car.
    The owner is silly, could have bought a modern used car.

    For your information:
    + swapped spark plugs countless time.
    + swapped coils a lot of time (new, used, used with new)
    + Compression is now the same for all the cylinder. (after head rework)
    + Ohm value for wiring of the injector is now the same for all the cylinder. (after repair wiring)
    + Catalytic converter found very clean

    Kompressor kicks correctly.
    MAF read ok.
    Tried at idle without air filter.
    Cleaned throttle body.

    Countless swear because of the poor design of airbox, hard to remove, breaks easily, had to repair once
    because we get DTC "air/fuel mixture adaptation" due to a crack in the airbox.

    If you leave airbox pipe out you also get DTC "air/fuel mixture adaptation".

    Sporadic DTC: RPM signal
    Forever (especially at idle) DTC: misfire cyl2.

    Before the head rework: Crank the car, leave it at idle, after 40 seconds engine begin to misfire.
    Before the head rework: Crank the car, push throttle and you can stay at 2500 RPM for minutes
    and engine could run regularly.

    Unfortunately, we didn't repeat this kind of test after head rework but be patient, car will return,
    and guess what DTC it will have.
    Last edited by alessioblaupunkt; 17th May, 2019 at 09:49 PM.
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    Meat-Head (26th May, 2019)

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    ON TOPIC:-

    About 4 years ago, was in church and the pope was talking about a misfire on an Audi A4
    not quite the same word for word, but plugs you could dance between, temp sensor broke, pipe split
    the choir boys did it all still miss fired. And cylinder ?? Miss fire.

    s0 the pope asked god for help, so he send a fax with some technical bulitin stating change AIR FLOW METER,
    the pope got the choir to change airflow, cured, then it rain d 24/7 for 40 days and nights.

    you could try a small amount of “duct tape” over intake to make it richer.

    also if you travel 30mph then floor gas pedal does it go like a rocket or bog down?
    Was Banned For Being Certifiably Insane and Stupid

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    alessioblaupunkt (4th June, 2019)

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    Does this have EGR. Classic symptom of EGR open a tiny bit.

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    alessioblaupunkt (4th June, 2019)

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    Quote Originally Posted by autoden View Post
    Does this have EGR. Classic symptom of EGR open a tiny bit.
    That would partly compute saying “air flow”. Is there a reset airflow counter?
    Was Banned For Being Certifiably Insane and Stupid

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    Car is in the street driven by old dude.
    If egr we can clean it if old dude cry for car not running ok.

    If "air flow meter" that will be money.

    That'll be good to change both and charge another 1500 EU/STER/US money.

    Nice the church storytelling.

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    Meat-Head (4th June, 2019)

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    Blank egr for test purpose

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    alessioblaupunkt (5th June, 2019)

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    Crook 02 sensor leaning out the mix when up too temp,
    Vacuum leak somewhere, brake booster leaking, some mercs ran vac too headlight adjusters, locks etc?
    A scope will allow you too easily check the injector drive waveform.
    I would be more inclined too say vac leak or an ignition component breaking down.
    My .02
    Cheers

    edit: ive struck injector issues a few times with em. swap a couple and see if your misfire moves... in fact id almost bet on a sticking one...
    Last edited by FordFanatic; 11th June, 2019 at 06:15 PM.

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    alessioblaupunkt (11th June, 2019)

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    "TOO" expensive "TO" repair

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    alessioblaupunkt (11th June, 2019)

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    On top of the head, near cyl 2, there is a vacuum pipe, our mechanic found it break,
    so he repaired it but still not solve the cyl 2 misfire.

    O2 sensor, brake booster, headlight, locks are nice hint.
    It's a nice idea to check the waveform of the injectors, I didn't do that because I didn't
    have a scope at that time.

    I figured now the church story has been heard 4 years ago, 4 years, just wow.

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    Meat-Head (11th June, 2019)

 

 

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