hi all i bought a focus rs mk1 3 weeks ago all is fine with the car up untill yesterday when i discoverd i had a misfire but it is only when you give it some beans (so to speak) it will pull no problem in 3rd upto 70 then will seem to hold back then when in top 5th it dont seem to want to go past 70 cleaned plugs (NGK NOT GENUINE FORD ONES ) and as most of you know cars like this dont run very well on after market plugs found out then that the ht leads were shot so replaced them today car now pulls much better but still got a small miss could this be down to the cheep plugs?? going to fords in the morning to buy a new set of genuine ford ones havanks any the any one on here had the same sort of problem with a rs ?? all help would be great full many thanks mark

 

Get on the rsoc and search misfire. Could just be the normal map. A lot of them misfire at 4000 rpm. Very common thing

 

It could be cheap plugs, the original Ford Motorcraft plugs will be fine.
Could be a coil pack problem or even timing related, but probably not...

It's also possible if the car is struggling to get past a certain speed/revs then the cat could be shot?

 

thanks guys but since fitted all new plugs/leads and now is running as it should be

 

Glad it is all sorted