I have noticed recently when I put my foot down I get a stutter at 4-5k revs. Only seemed to be on this recent tank of fuel. It seems to be: 1. With sport button pushed. 2. Between 4-5k Rpm 3. In Gear 3 above. Is there boost by gear? Does not happen every time. Now the car is a Megane 275. 6 years old. 22k miles. Just had service about 2 months/3k ago with Cambelt /plugs/oil/filters everything for the 6 year service. And is running best economy every on a run easily over 40mpg. Had a big trip to Scotland 2 months ago where I did 2k in a week. All steady motorway miles with low revs. Only done 500 miles since then. But I do hardly any miles. Typically 200 miles in a month and then a couple of big runs in the year. So fuel gets to 3-4 weeks old before I fill half a tank ( Sains Super so 97 Ron/E5). May sit 4-5 days then be used for school run in very heavy traffic. Say 3 miles taking 30 mins. With Stop/Start potentially kicking in. In between I may move about on my drive. Start. Move. Stop. I looked on line and it says things like thermostat, coils, fuel filter, plugs/gap. Does it just need driven hard to get everything warm and worked through? Multiple pulls to hard revs. "Italian Tune Up" I am getting down this tank so will run it down & put some proper 99 see if that makes a difference.
As you say I would maybe run down the tank and put a full tank of v power or similar and see if the slight misfire dissappears. Was it all genuine parts used when it was serviced plugs/etc ?
My mate had a slight misfire intermittently in his 265 and after his thermostat was changed the misfire was no longer present. He had a issue with his secondary coolant pump that was also rectified at the same time. His car runs alot better now.
Misfire got much worse at weekend and threw up a code for Misfire on Cylinder 2. It turned out to be a Crack in the plug. The Mechanic that changed them though they looked older than the 3k/6 months they had been in because of the ceramic discolouring. But the actual electrodes look good even the one on the duff plug. Never seen iridium plus before. Spikey.
Also had a lumpy idle fluctuated 100 rpm up & down when cold. Now very steady. Did the Coils as well as plugs.
