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Bad/Damaged Piston #3???

Discussion in 'General Tech and Maintenance' started by utn, Dec 29, 2004.

  1. utn

    utn Member

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    I always knew something was up with my piston, especially when i saw black oil inside of the exhaust port (when I removed the headers). But now I noticed that if I unplug the spark plug wire to that cylinder there is NO change in engine sound or speed (uh-oh). My ECU never gave me any codes as to a cylinder malfunction and I always thought I had a bad valve seal, but I guess I was wrong. How can I target the problem, or see if I can get the cylinder firing again? Should I do a compression test or what?

    Thanks,
    Scott


    P.S. Its a 89 CRX DX with a B16A swap OBD0
     
  2. civicious

    civicious FüK-VTEC VIP

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    Replace your spark plugs. The plug to that particular cylinder is bad, I'd almost be willing to bet money on it. If you switch the bad plug (say it's cylinder 1) with the plug from cylinder 4, you'd probably find that cylinder 1 is fine, and cylinder 4 has liquid in the inside of the exhaust port. This is because the plug isn't firing, and the gas isn't burning up.

    You also might notice that when you remove the spark plug from the cylinder in question, that the tip of the spark plug looks wet. Compare it to the other plugs, the other plugs will probably look dry and burnt.
     
  3. liquidhg

    liquidhg Junior Member

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    I agree with the previous post in that it is possible that the plug may just be bad, and that may be causing #3 not to fire. But allow me to share my own anecdotal expierence. As we speak, my car is in the shop having one of my pistons/rings replaced after it melted from running too lean. I would sugest that you do a compression test - it takes less than a minute to do. That will tell you if you fried or broke a ring. I hope that in this case the problem is due to a lack of spark. Melting a piston, or breaking a ring is a pain in the ass to fix.

    What mods have been done to the car? Just the swap?
     
  4. utn

    utn Member

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    Thank you for the speedy response. I am going out today to purchase 4 brand spankin new spark plugs, and I'm going to do a compression test, does anyone happen to know offhand what the PSI should be in a B16A cylinder? My engine also gives me a bit of blow by gasses (or so I have been told). If I disconnect the blow by gas tube that goes to my intake i see a little bit of gray smoke, and it smells like gas, could this be because of cylinder 3 with its possibly faulty spark? Or is this bad piston rings?

    Thanks again,
    Scott
     
  5. reckedracing

    reckedracing TTIWWOP VIP

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    i also advise a compression test and leakdown test...

    you can also pull the wire and put a spark plug to it and ground it to see if its not a wire/distributor problem...


    if its getting spark to the plug and you changed the plug in the cylinder then its either no compression or no fuel...
     
  6. utn

    utn Member

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    I did a compression test on Cylinder 3 and i got ~60 PSI :( I tested #2 and got about 150 PSI if i remember correctly (didnt bother to test the others, but will eventually, they seem fine). Will #3 give me any power if the spark is firing correctly with the injector working well too?

    Thanks,
    Scott
     
  7. liquidhg

    liquidhg Junior Member

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    No
     
  8. liquidhg

    liquidhg Junior Member

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    Allow me to elaborate

    You have to keep in mind that if your compression is that low it is due to a poor seal between your piston and cylinder. PSI is a linear measurement, meaning that a chamber filled with air and at a pressure of 20 PSI is twice the amount of air as the same chamber filled with air at a pressure of 10 PSI. Another way to think about it is if you take a quantity of air at a set volume, and compress it down to half it's size, the pressure will double. If you are getting pressure readings of nearly 1/3 that of your working cylinders, then the number 3 cylinder has 1/3 the air fuel mixture.

    Also keep in mind that there are 4 important steps/strokes to internal combustion:


    Intake stroke
    Compression stroke
    Combustion stroke
    Exhaust stroke


    During the compression stroke you are loosing nearly a third of your air fuel mix, and also loosing much of the compression that is necessary to create a powerful explosion within the cylinder.

    So basically.. you are only really getting power on 3 cylinders, you are more than likely burning/loosing oil, and you really need to get some engine work done. If one of your rings is broken, and a part is flying around inside your cylinder you could end up causing a great deal of damage to your head, and block.
     
  9. utn

    utn Member

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    Just now I took out the spark plug for that cylinder, altered the gap of the plug a little and cleaned it off a bit and reinstalled the plug. The engine ran a lot smoother and had significantly more power than it did a few hours ago, I know its not nearly what it should be and that it is a serious problem, I am going to get it fixed very soon.

    Thank you for the quick and late night response,
    Scott
     
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