Pretty new to the ST world and have picked myself up a tidy looking 2003 Focus ST170. the car is as i had hoped except one thing. A terrible Misfire. This issue seems to be when I accelerate and as the engine is faced with a greater demand for power (as the revs build past 4000 rpm) the engine seems to really struggle and misfire. This is so disappointing because I can only imagine how quick the car can be and not actually feel it. Even more so as this is my second car and the one I planned to do a few track days in this summer. The misfiring seems to also occur, although less frequently at lower revs in 4th and 5th gear when you accelerate.
I will be checking the spark plugs this week and I am dubious as to whether its the Injector cylinder (the long thin cylinder and the back of the bulk head. But these are both theories and having done 115000 miles I am very worried I require an engine rebuild!
ANY HELP would be massively appreciated.

Thanks

 

Did you get any joy with this problem as I'm havin similar problems only its when I've slowed down and say turn a junction n try pull away in 2nd and get a big misfire

 

I havent had any luck yet unfortunately. I have changed the HT leads and weather permitting I am changing the Fuel tank, pump & Driver console this weekend. Thats purely based on what I've read on other forums though. Also the coil pack has been the issue for a number of people?
My next step is to take it to a place in blackpool that do a very thorough fault finding on the car using a rolling road and measuring the fuel-air mix of the car!
I will let you know if I have any success