Hi,

I have a C-max 1.8 2007 mk1 showing 112000 miles, just had a full service, oil and filters, air filter and new plugs, to try and get rid of a problem im having at low revs between 800 and 1200 rpm's, today i have also had the air filter box off and sprayed some wd40 fast drying contact spray through the air intake throttle valve, slight improvement i think, but it hard to be sure, cant see an EGR valve or i would remove and clean that next, also added REDEX to two full tanks of fuel, going to try the more expensive fuel next just in case, also considered a remap, dont know enough about petrol cars to hazard any more guesses as what to try next, other than taking it to a garage for a diagnostics doctor for a full examination, so any advice on what to try before i do this would be gratefully appreciated.

P.S the problem im having is it is juddering and hesitant within that range, but not 100% of the time, and improves slightly when warm, i have a 1.6 version too and that is smooth and no problems

Have you had the leads changed? Check their resistance with a meter to check them.

https://www.ngk.de/en/technology-in-detail/ignition-cables/diagnosis/testing-of-ignition-cables/