Loss of Power in Honda City ZX GXi! Help Needed.


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As many of us would have seen, piston rings are not a continuous circle. They have a cut, so that it can be mounted in the piston ring grooves. When in place and piston sliding in the cylinder, there still is a gap in the piston ring ends. Why? To make sure when they expand after getting heated up, they dont start touching each other and force the ring to break. In bigger engines, this clearance is checked. It is called Butt Clearance. It is very important to have a certain minimum value of this clearance, else the rings will break or damage the cylinder in no time. In cars, it is very difficult to measure this. I dont know whether it is measured or not.
How do piston rings seal? First of all, they are manufactured in such a way that they maintain their spring action throughout there life. And gas pressure plays a vital role in sealing process. Gas enters the groove and pushes the rings outwards, ensuring proper sealing during power stroke. Inspite of all this, there always is slight leakage of gas into the crankcase. This is the reason why carbon content in oil increases with usage/time.
 
Thread Starter #17
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Thanks everyone for the input.

I took the car to autozone today with my mechanic and did compression test again just to confirm the initial findings but the reading i got today was alltogether different from what i got earlier on.Compression in all the cylinders showed very low reading, as a result my mechanic is now suggesting engine needs minor overhaul to replace piston rings and other parts which will cost approx Rs.20-25000. I am thinking of selling the car now instead of forking out so much time and money on a 5 year old car with almost 1 lakh oddo. It has already given me enough headache over a couple of months now.
 
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Finally you found the culprit. A correct compresion test at the first instance would have saved you from so much of headache. Reduced compression pressure can be because of various reasons. If you can trace the real reason, maybe you can be saved from spending huge amounts.
At 1 lakh, piston rings going bad is a rare occurence, unless you have illtreated her during her lifetime. Since changing of piston rings requires dismantling the engine completely, I would suggest you few checks before you go for complete decarb or sell off your car.
  • Please check the condition of engine oil. On touching, do you feel high carbon content (It will feel more viscous than oil under normal condition). If piston rings are gone, engine oil condition will give you clear picture.
  • Another goof up could be bad adjustment of valve tappets. If clearance is less than recommended, the valves wont seal when temperature rises up, and you'll feel lack of power. Do consider rechecking of valve adjustment. This option will be much cheaper than piston ring renewal. Also after this test you'll be sure of your next step (sell/retain the car). But do get it done from a reliable place.
There could be few other reasons. But in your case, I feel these 2 or most relevant. And I very much feel, tappet adjustment would solve your problem.
Please note, if you run your car in this condition for prolonged time, the valve & seat are liable to get damaged, and you'll need to change/ lap them.
 
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