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Thread: 100,000 mile compression test/spark plug replacement!

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    Senior Member Cobrajet's Avatar
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    100,000 mile compression test/spark plug replacement!

    Well, 97,516 miles to be exact.

    I always wondered how this engine was holding up to what I was subjecting it to, and decided that if I was going to have the plugs out for replacement anyway I might as well do a compression test. Technically, the plugs are not due for replacement until 105,000 miles. But I also decided that if I was going to check the condition of the engine it should be done just before the warranty expires, not just after.

    You will need:

    1) Compression tester. These can be rented at any auto parts store.
    2) Ratchet.
    3) 10mm socket.
    4) Spark plug socket (the smaller one of the two).
    5) 6" ratchet extension
    6) Replacement spark plugs. I went with the Denso IKH16TT.
    7) Silicone dielectric grease.
    8) That's it!



    The compression test should be done with the engine HOT OR WARM, since this is it's normal operating condition. So warm the car up.

    The first thing you will remove is the baffle on the side of the air cleaner housing. There is one 10mm bolt that holds it on, and you should be able to wiggle it out of the side of the housing by pulling it to the left.



    The next thing you will remove is the air cleaner housing. There is one bolt on the left side..



    ...and one on the back.



    The air cleaner housing can be separated and the filter removed. The rear section of the housing is secured on the bottom to the top of the valve cover by a rubber grommet. Wiggle it up and out.



    The PCV hose is clipped onto the right side of the air cleaner housing. Simply pull it free.



    The intake hose can be removed with the 10mm socket by loosening the lower clamp. Pull it free.



    There is one electrical connector to disconnect at the housing for the Intake Air Temp Sensor...



    The front of the air filter housing can be swiveled out of the way and rested on the battery, or you can disconnect the PCV hose with pliers and remove it completely. The coil packs should now be visible. Each is retained with one 10mm bolt, painted orange.



    Remove the coils by removing the bolts and disconnecting each of them. Wiggle them up and out. I would keep them in the order they were removed so they can be reinstalled on the cylinder they came off of.



    Removing the spark plugs is pretty self-explanatory. Just unscrew them. If you are planning to replace them they can be discarded. If you are going to reinstall them, keep them in order so you can put them back into the appropriate cylinder.

    Once all have been removed, disconnect each fuel injector connector at the fuel rail. This will keep the PCM from fueling the cylinder, as excessive fuel in the cylinders during the test will wash the cylinder walls and affect the readings.



    Okay, you are ready to start the test! Screw the tester securely into the #1 spark plug hole. Get into the car, FLOOR THE ACCELERATOR, and crank the engine over about ten times. You need to floor the accelerator to allow the throttle body to open wide and allow as much air to enter as the cylinder needs.

    You should get a reading like this on the tester...



    ...and #2...



    ...and #3.



    And there you have it! On my motor the results are read as:

    Cylinder #1: 195 psi
    Cylinder #2: 195 psi
    Cylinder #3: 190 psi.

    Factory specs are 205 psi for a new motor. The readings here indicate that at the end of my powertrain warranty this is still a healthy motor! This engine got no Superman maintenance...just by the book. Mobil 1 0w-20 AFE full synthetic every 7,500 miles...religiously. Plugs looked like you would expect 100,000 mile plugs to look.



    Reassembly is the reverse of disassembly. My coils were sticky coming off, so I put some dielectric grease in the ends when reinstalling them.

    When I started the car after reassembly, the check engine light was on. It gave me a code P0113, which is for the disconnected IAT sensor. I am not sure if this code will self-resolve over time, but I just reset mine with an OBDII reader. Any auto parts store will reset the code for free.





    And there you have it. Please post up your readings if you do a compression test. Let's see how tough these little three-holers are.


    Last edited by Cobrajet; 07-10-2018 at 09:52 AM.

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    Senior Member Top_Fuel's Avatar
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    Great write-up!

    How is your car doing with oil consumption? Are you adding any oil between your 7500 mile oil changes? I'm just wondering if these engines will tend to start using more oil as the miles rack up. I've never heard anyone with a high-mileage Mirage with comment about it.

        __________________________________________

        click to view fuel log View my fuel log 2015 Mirage ES 1.2 manual: 51.9 mpg (US) ... 22.1 km/L ... 4.5 L/100 km ... 62.3 mpg (Imp)


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    Senior Member Cobrajet's Avatar
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    Quote Originally Posted by Top_Fuel View Post
    Great write-up!

    How is your car doing with oil consumption? Are you adding any oil between your 7500 mile oil changes? I'm just wondering if these engines will tend to start using more oil as the miles rack up. I've never heard anyone with a high-mileage Mirage with comment about it.
    She has started to use about 1/3 of a quart between changes. Nothing I'd consider surprising.

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    Quote Originally Posted by Top_Fuel View Post
    Great write-up!

    How is your car doing with oil consumption? Are you adding any oil between your 7500 mile oil changes? I'm just wondering if these engines will tend to start using more oil as the miles rack up. I've never heard anyone with a high-mileage Mirage with comment about it.
    Our highest mileage car (238000miles) started using about 1/2 liter every 7500 mile oil change. Not too bad. I changed the plugs around 100k miles too and they looked great no carbon buildup at all, the electrode was slightly worn but barely noticable. This car has been replaced by a van and is now used for mostly in town runs. I'll try to do a compression test next oil change.
    My mom says I'm cool

        __________________________________________

        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)


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    Well thats good news, I only have 4400 miles on my '18 but good to see they are still strong at 100,000. What was the normal habit for the car? City/highway
    2018 mirage ES manual

        __________________________________________

        click to view fuel log View my fuel log 2018 Mirage Es 1.2 manual: 41.6 mpg (US) ... 17.7 km/L ... 5.7 L/100 km ... 50.0 mpg (Imp)


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    Great write up and its great to see your engine holding up so well.

    I've added this to the mods list.
    Custom Mirage products: Cruise control kit, Glove box light, MAF sensor housing, Rear sway bar, Upper grill block

    Current project: DIY Nitrous oxide setup for ~$100

        __________________________________________

        click to view fuel log View my fuel log 2015 Mirage DE 1.2 manual: 47.2 mpg (US) ... 20.1 km/L ... 5.0 L/100 km ... 56.7 mpg (Imp)


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    Senior Member Cobrajet's Avatar
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    Quote Originally Posted by Timinator View Post
    Well thats good news, I only have 4400 miles on my '18 but good to see they are still strong at 100,000. What was the normal habit for the car? City/highway
    All city.

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    Quote Originally Posted by Cobrajet View Post
    When I started the car after reassembly, the check engine light was on. It gave me a code P0113, which is for the disconnected IAT sensor. I am not sure if this code will self-resolve over time, but I just reset mine with an OBDII reader.
    Thanks for the write-up, Cobrajet. I have some questions for you:
    1. Has the P0113 code given any further problems?
    2. Any other noticeable change in operation?
    3. What brand gasoline do you usually use?

        __________________________________________

        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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    Senior Member Cobrajet's Avatar
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    Quote Originally Posted by Eggman View Post
    Thanks for the write-up, Cobrajet. I have some questions for you:
    1. Has the P0113 code given any further problems?
    2. Any other noticeable change in operation?
    3. What brand gasoline do you usually use?
    1) Nope. Once cleared with my OBDII reader it was gone. It was simply the result of cranking the engine with the IAT sensor disconnected.

    2) A slight change. I also put some injector cleaner in at the same time. First time I had done it. I went to Costco and they had a box of six bottles of Techron injector cleaner for only $14! Mpg seems a tiny bit better and idle seems a little smoother, but I don't know if it's the new plugs or the injector cleaner doing it's thing. I checked the electrode gap on the original plugs, and at "0.050 they were still within specs. Probably could have left them in, as I expected.

    3) I use top-tier...either Arco or Mobil, with a few dozen tanks of Chevron and Texaco mixed in. This car gets good enough mileage that I don't feel I need to cheap out on gas!

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    Quote Originally Posted by Cobrajet View Post
    1) Nope. Once cleared with my OBDII reader it was gone. It was simply the result of cranking the engine with the IAT sensor disconnected.

    2) A slight change. I also put some injector cleaner in at the same time. First time I had done it. I went to Costco and they had a box of six bottles of Techron injector cleaner for only $14! Mpg seems a tiny bit better and idle seems a little smoother, but I don't know if it's the new plugs or the injector cleaner doing it's thing.
    This is interesting. Anyone else could try the Techron treatment. Hmmm - I think we're due for a Costco run.

    Quote Originally Posted by Cobrajet View Post
    I checked the electrode gap on the original plugs, and at "0.050 they were still within specs. Probably could have left them in, as I expected.
    This could be another point of visual inspection I've been thinking over. Pull the plugs and inspect their gap & condition. Also visually inspect the combustion chamber with a camera while the plugs are out, and of course a compression test. Your write-up makes it look easy. I wonder if the injectors are as easy to access and remove, and it it's worth an occasional inspection.


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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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