I have had 2 renault lagunas 1.8 8v R plate and 1.8 16v W plate and both began mis-firing around 60k, turned out to be engine ignition coils in both instances, car sounded ropey and did not respond when put under load. Also at the same time on the R plate Laguna the oxygen Lambda sensor was faulty, adding to the misfire and loss of power.
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