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Discussion Starter #1
hey everybody and happy new year! i have a 2000 honda civic 1.4 and i noticed the other day it has a rattle/knocking noise when you first start it up. you can only hear it on the over-run after reving it and then the rattle/knock will stop as it approaches idle speed. this will happen for a couple of minutes until the engine warms up a bit. after that the car seems to run relatively smoothly, doesnt use any oil or fluids and doesnt smoke. if anybody has any idea what this could be, whether its general wear and tear or something that may get worse i would be grateful to know! thanks dan
 

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Discussion Starter #3
thanks for your speedy reply. im affraid im unsure at present as i have just recently discovered it, my dad was the last person to drive the car and he suspects it probably was producing that noise under light load when cold, im sorry if this discription is quite vague. thanks dan
 

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well with your description it sound like piston slap,
this happens at the times and loads you are talking about
and dissapears when warm say 5 minutes max
its the pistons slightly worn in the bores and twisting slightly on there way up and down the bore
it goes away because the piston expands slightly and the noise then goes.

i have had a couple of cars do it and it can go for years without ever getting worse depending on how noisy it is obviously
and its not an exact science as nothing with wear and tear is,
just warm it up nicely as you should anyway.
 

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Discussion Starter #5
thanks paul your reply has been very helpful, im not too worried about it but i wanted to know what it was all the same, thanks again, dan
 

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The tapping noise is the piston skirt tapping the cylinder wall at TDC, this can happen with shallow pistons, it doesn't affect the engine performance and won't wear the bores, but like paul20v suggests take it easy on warmup. I had a Rover K series with 32k miles that did it, it was always worse on frosty mornings, my 1.4 EJ9 has a little piston slap too on first startup. My last car a Yaris (don't ask!) had a tapping when cold that tuned out to be a leaking manifold gasket, the noise I could hear was the exhaust valve seating, sounded very similar to piston slap and went away when the engine warmed up. The clever Toyota ECU compensated for the loss in pressure so the idle speed didn't alter!
 

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Phatman said:
The tapping noise is the piston skirt tapping the cylinder wall at TDC, this can happen with shallow pistons, it doesn't affect the engine performance and won't wear the bores
your 100% right on the skirt i did not want to go into so much detail but it is a sign of wear on a lot of engines that didnt do it and now do,
its a piston/bore wear more piston and yes shallow pistons are more prone to it for obvious reasons.
But its not a major issue.
 
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