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

  1. #71
    Moderator Eggman's Avatar
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    Hey foama would you please describe how you captured those images of your valves? I would like to try this.


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        click to view fuel log View my fuel log 2015 Mirage ES 1.2 manual: 49.7 mpg (US) ... 21.1 km/L ... 4.7 L/100 km ... 59.7 mpg (Imp)


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  3. #72
    Senior Member HitShane's Avatar
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    Quote Originally Posted by Eggman View Post
    Hey foama would you please describe how you captured those images of your valves? I would like to try this.
    Quote Originally Posted by foama View Post
    Yes, took the pix today with a USB endoscope. They're sold by Weepay and other sites for around 10-15 bucks.

    Taking those pictures was easy. I just took the block with the three injectors out (two bolts), and stuck the endoscope through each injector hole for looking at the valves, and took pictures. Afterwards thoroughly cleaned and lightly lubed the O-rings and put all back together. Real easy to do, took no more than 10 mins.
    Like this.

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    Senior Member chris_top_her's Avatar
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    Quote Originally Posted by Eggman View Post
    Hey foama would you please describe how you captured those images of your valves? I would like to try this.
    Something like this if you have a android phone http://www.ebay.com/itm/5-5mm-Androi...Za4AGsJicVnm8Q
    they also have them for iPhone and some with wifi to connect to the phone. Or a usb type for laptop.

  6. #74
    Junior Member Dabullfrog91's Avatar
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    I got a couple of questions for everyone. First off, how quick are these cars and will driving them faster cause this issue? I rarely if ever even do over 80mph (128.75 kph). Usually I am between 65mph and 75mph on the interstate. Also, I am currently only using unleaded fuel over here in the states. Since this is a high compression engine (I have the 1.2 i3) should I be using only premium grade fuel? My car seems to run just fine on regular unleaded but I don't want to take any chances of something like this happening to mine. My thoughts however on why this issue happened (like so many others on this post) would be that the fuel had to have something to do with it. Perhaps we use more detergents in our gasoline here in NA? So maybe lack of detergents caused the quick carbon buildup on the valves?

  7. #75
    Moderator inuvik's Avatar
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    It's the lack of a EGR in the 3A90 1.0 that is a contributing factor for the carbonization along with most likely some bad fuel. This has been a non-issue with the 3A92 1.2. No need for premium, regular grade fuels are just fine. Many members report they drive their Mirages pretty hard all the time with no issues. Just keep driving like you always have been. As far as how fast will a Mirage go? A few members drive 80+ all the time and yes triple digit speeds are possible.

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        click to view fuel log View my fuel log 2015 Mirage ES 1.2 automatic: 40.4 mpg (US) ... 17.2 km/L ... 5.8 L/100 km ... 48.5 mpg (Imp)


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    I'm with inuvik, putting premium in a mirage is a waste of money. They run fine here on 87 octane.

        __________________________________________

        click to view fuel log View my fuel log 2014 Mirage SE wussie cvt edition. 1.2 automatic: 37.4 mpg (US) ... 15.9 km/L ... 6.3 L/100 km ... 44.9 mpg (Imp)


  10. #77
    Quote Originally Posted by Dabullfrog91 View Post
    I got a couple of questions for everyone. First off, how quick are these cars
    Not "quick", relative to most cars in the US.

    Thread: Mirage acceleration times: 0-62 mph / 0-100 km/h and top speed (1.0L & 1.2L engines)

        __________________________________________

        click to view fuel log View my fuel log 2014 Mirage SE 1.2 manual: 66.3 mpg (US) ... 28.2 km/L ... 3.5 L/100 km ... 79.6 mpg (Imp)


  11. #78
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    Re-posted, originally posted last year:

    Quote Originally Posted by foama View Post
    Yes, took the pix today with a USB endoscope. They're sold by Weepay and other sites for around 10-15 bucks.

    Taking those pictures was easy. I just took the block with the three injectors out (two bolts), and stuck the endoscope through each injector hole for looking at the valves, and took pictures. Afterwards thoroughly cleaned and lightly lubed the O-rings and put all back together. Real easy to do, took no more than 10 mins.

  12. #79
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    @Dabullfrog91: The carbon incident of 2016 (see first post) was a freak event. It happened to mine and several other identical cars that filled-up at two particular fuel stations. No similar problems since, and the valves remain clean ever since.
    How fast? These cars don't have much acceleration, but are fast enough to keep up with the average traffic in the fast lane of the German Autobahn, and thats fast enough for me.


    UPDATE September 2018:

    The valves look clean, just as clean as last year.

    The cause for the incident must have been a tank full of bad fuel.


    UPDATE September 2019

    Valves look just as clean as ever. Perfectly clean, just as inside combustion chambers.

    However, ever since the car was "repaired" and carbon removed, the compression has been much lower at around 9bar (about 130 psi) on all cylinders, and fuel consumption is consequently about 10% or so higher than before.
    This car has a compression ratio of 11.5 : 1 and so compression should be much better.



    UPDATE August 2020: IT HAPPENED AGAIN!

    Until very recently the valves looked clean as new. It now happened again! Last week the car wouldn't start. It had been resting in the garage for a few days after a long drive on the autobahn, just as in the first incident in post 1. A quick compression test showed almost nill compression on two of three cylinders, and very low on the third. Looking with the endoscope the intake valve stems were seen full of brown or black-brown gummy sticky goo and therefore could not close all way. Valves open means no compression means no start.

    Since the warranty had expired years ago, I repaired it like this:
    The intake manifold was removed and three new aftermarket gaskets manifold-to-head bought.
    I stuffed a narrow strip of cotton rag saturated with acetone into the intake hole leading to the valves of the first cylinder and added some acetone to it about every few minutes. After a half hour or so removed the rag and saw the gunk had softened. With a bundle of cable ties wrapped together as a tool, the gunk was mechanically scratched off, adding a little acetone every minute or so while doing it. Put the rag back into the intake, repeatedly added acetone, repeated the entire procedure again a few minutes later. Did the same on the second cylinder. When turning over the engine by hand, I could tell the valves were now moving properly. Some of the goo was still there, but most gone and the remaining much softened. Put everything together quickly, started the car and drove off to fill up the half empty tank with some fresh fuel. Checked it a few days later and everything looks perfectly clean again. Compression is unchanged as after the first warranty "repair" see first post of the thread.

    A chemical engineer explained to me that E10 fuel (10% alcohol) plus acidic greasy combustion products cause exactly that sort of residue. I didn't really understand what he said, but understood it had something to do with chemical reactions, the higher alcohol content of the fuel, and the blow-by reentering the intake. Although the car uses practically no oil, I ordered a little catch can that might help condensing some of those combustion byproducts. It will be intalled in the 10mm hose between valve cover and intake manifold. I wonder if it makes any difference...
    Last edited by foama; 08-02-2020 at 08:19 AM.

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    UPDATED August 2020

    It happened again!

    See post above for details and how it was repaired.



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