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Thread: 3A90 Intake valves stuck open, carbonized, full of gunk and car won't start

  1. #1
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    3A90 Intake valves stuck open, carbonized, full of gunk and car won't start

    I'm asking if anyone else has experienced such problems with the 3A90 (1.0 L) engine. Please report!

    My car has about 20 000 km on it, and is only used for long-distance driving. It had no history of any problems at all. The engine is 1L, 3A90, no AS&G and consequently no EGR. Remember, this is a non direct fuelinjection engine, fuel is injected before the combustion chambers and not into them.
    Coming home after a 300km drive on the autobahn, driving at 100 - 130kmh, the car was parked in the garage. Next morning it refused to start, but cranked normally and began smelling like fuel.

    After telling the dealer about the problem, he said it would take 3 or four days in the workshop, but perhaps longer, and
    Mitsubishi would see the bill taken care of. After all, the car is under waranty and there is a mobility garantee.

    I asked him how he could tell without having even seen the car. He replied he'd already seen numerous with that problem in his tiny workshop...

    On the following day using a mini endoscope camera, the dealer confirmed the problem. The intake valves were not closed because of massive "gunk" or carbon deposits all over the intake valves.The massive buildup did not allow the valves to close, and without closed valves no compression, no starting. He reported the problem to Mitsubishi, asked for permission to perform the waranty repairs, and ordered the parts Mitsubishi allowed him to replace.
    The next day the cylinder head was removed, valves removed and cleaned manually. The removed carbon deposits were "hard as rock". The original valves were to be put back in and grinded in the late afternoon or next day, which is tomorrow.

    I will keep you posted on this matter, but am travelling throughout Europe and don't always have Internet.



    Update:immmediatly after repair:
    It seems this issue is not uncommon in 3A90 engines.
    A local service-provider with five or six SpaceStar's has seen the same problem at least once with each one, albeit at maybe half the milage. Their Space Star (Mirage) are used for short-distance customer to customer hauls, and are equipped with AS&G. The A390 with AS&G supposedly have EGR, the non-AS&G don't.

    The dealer said, there will come a new software for these engines sometime in the unspecified future, which should address and hopefully remedy this problem. Currently no new software is available for this car yet...


    UPDATE, March 12 2016

    1) The dealer briefly showed me a picture of badly fouled exhaust valves, but did not let me take either the photo with me or to photograph or copy it. He said:"The picture (supposedly of my car's valves) is Mitsubishi property and may not be disclosed, copied or given away!"
    2) Since the repair, I have noticed higher fuel consumption and lower top speed. Driving to work the bult-in display showed around 4.3 to 4.5 L/100km before repair, and now afterward always more than 5L/100km, usually about 5.2L/100km. The top speed on a flat autobahn with no wind was displayed at around 172-175kmh according to the car's speedo. Now it reaches around 160kmh under the same conditions.

    After visiting the dealer about this, I was told new software was flashed into the ECU.

    I hope to find out more, or get the situation resolved.
    I will post updates.


    Last edited by foama; 03-12-2016 at 02:52 PM.

  2. The Following 4 Users Say Thank You to foama For This Useful Post:

    Eggman (01-05-2016),inuvik (01-05-2016),MetroMPG (01-05-2016),RodeRoNL (04-24-2017)

  3. #2
    Administrator Daox's Avatar
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    Interesting. You're the first I've heard of this on the 1.0 or 1.2L engines.

        __________________________________________

        click to view fuel log View my fuel log 2015 Mirage ES 1.2 automatic: 49.0 mpg (US) ... 20.8 km/L ... 4.8 L/100 km ... 58.8 mpg (Imp)


  4. #3
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    The carbon is a symptom, not the problem.

    regards
    mech

        __________________________________________

        click to view fuel log View my fuel log 2015 Mirage de 1.2 manual: 55.7 mpg (US) ... 23.7 km/L ... 4.2 L/100 km ... 66.9 mpg (Imp)


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    cyclopathic (01-06-2016)

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    Administrator MetroMPG's Avatar
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    Thanks for the report, foama. Please keep us updated.

    I'm sure the garage has a theory about what caused the build-up.

        __________________________________________

        click to view fuel log View my fuel log 2014 Mirage base ES 1.2 manual: 54.0 mpg (US) ... 23.0 km/L ... 4.4 L/100 km ... 64.9 mpg (Imp)


  7. #5
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    No other symptoms of increasing restriction to intake flow, even at 130 kph on the last drive?

    Then the next day there is not enough compression for it to start?

    Doesn't sound right to me. Did it idle right when you got home from the trip? Other symptoms?

    regards
    mech

        __________________________________________

        click to view fuel log View my fuel log 2015 Mirage de 1.2 manual: 55.7 mpg (US) ... 23.7 km/L ... 4.2 L/100 km ... 66.9 mpg (Imp)


  8. #6
    Moderator inuvik's Avatar
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    Interesting, lack of cleaning chemicals in the fuel an issue in Europe? I normally run some Marvel Mystery Oil in my fuel on occassion but maybe I'll add some Seafoam next tank

        __________________________________________

        click to view fuel log View my fuel log 2015 Mirage ES 1.2 automatic: 40.7 mpg (US) ... 17.3 km/L ... 5.8 L/100 km ... 48.9 mpg (Imp)


  9. #7
    Moderator Eggman's Avatar
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    I've heard of this problem on the direct injection engines.

    Could an oil leak cause this?

    Maybe these cars are not so great after all.

        __________________________________________

        click to view fuel log View my fuel log 2015 Mirage ES 1.2 manual: 49.3 mpg (US) ... 21.0 km/L ... 4.8 L/100 km ... 59.3 mpg (Imp)


  10. #8
    Moderator inuvik's Avatar
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    Quote Originally Posted by Eggman View Post
    I've heard of this problem on the direct injection engines.

    Could an oil leak cause this?

    Maybe these cars are not so great after all.
    We have a lot of members with way more mileage than this without a issue. My best guest would be overfilling the crankcase at oil changes, resulting aeration of a lot of oil. Causing a bunch of oil to pass through the PCV which of course would cause carbonization.

        __________________________________________

        click to view fuel log View my fuel log 2015 Mirage ES 1.2 automatic: 40.7 mpg (US) ... 17.3 km/L ... 5.8 L/100 km ... 48.9 mpg (Imp)


  11. #9
    Senior Member ahausheer's Avatar
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    You would need a serious amount of blowby on a port injected engine to create such a problem at 20,000 km (12,500 miles!!). At such low mileage and seemingly mild driving I would suspect something else is at play. I would be curious as to the condition of the EGR and the PCV valve. Perhaps you can pull the rubber hose off the PCV valve and let us know if it has lots of oil in it and/or any other problems reported by the dealer. Thanks for reporting.
    Last edited by ahausheer; 01-06-2016 at 02:37 AM.

  12. #10
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    Get rid of whatever is in the fuel tank, if they just clean up the residue. Reminds me of what happens when someone puts sugar in your gas. Had it happen to a customer in the Navy. We did a valve job on his 240Z, he was deployed and left the car sitting for a year. Got back a drove it and every intake valve stuck open. The goo was like cooked caramel. Pulled the head, cleaned the valves reinstalled everything and drained the tank and refilled. Never had the problem again. Job done gratis even though it was definitely not my fault. Good customer who spent money on his car, had the seals and gasket in stock.

    regards
    mech


        __________________________________________

        click to view fuel log View my fuel log 2015 Mirage de 1.2 manual: 55.7 mpg (US) ... 23.7 km/L ... 4.2 L/100 km ... 66.9 mpg (Imp)


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