Megane mk2 running rough

Could be coming from the rings instead of the valves-get a cylinder leakage test to confirm where the compression is leaking at

Thanks razmataz for the speedy reply I have got to take it this afternoon for the cylinder leakage test to be done so will know soon if pistons rings are causing the problem .

Well all I can say wot a flaming fiasco , I sent my fella to the Renault specialist who originally done the compression test last week I stated on the phone I wanted a cylinder leakage test and he agreed he could do this test for 25 quid but when my fella turned up this afternoon he told him he could only test the piston rings if he took the cylinder head back off . And he would do another compression test he did it at a cost of 30 quid he tol him compression on cylinder 4 was now at 175 psi which last week he said would be acceptable but this week he said its not and my nephew would need to strip it back down and send it off to be machined as u can't do valve work at home so were still no further forward as I have looked on the Internet myself and read myself that the leakage test is done through where the spark plug is I have come to the conclusion that this mechanic specialises I bull shyte

A quick update for you all my nephew stripped the engine down today removed the piston from number 4 where we had reduced compression , and as soon as it was pulled out the piston it started falling to pieces it was totally bladdered so we have ordered a new piston and rings for today and he will be putting it all back together thanks for steering us in the right direction :)