Hello,

Hoping someone can help, I have an 05 Festat ST with 53k on the clock and it has developed a misfire when over 4k the car judders and you can hear it missing. When idle there is a slight burble but not that noticeable. Also when you blip the accelerator idleing it hold the rev’s for a split second before settling back down. So far it has not done it under 4k.
I have cleaned the induction kit and the throttle body, I have had the plugs out and they seem fine a little black but nothing uninspected.
Any ideas what it could be? I was thinking coil pack but that would miss all the time?
Thanks,

 

Coil pack and/or plug-leads .... two best bets imo mate.

What mods do you have?

BR
Thomas

 

Thanks for the reply,
I was thinking coil pack but everyone is saying it would do it all the time. Iv got a 4-1 miltek manifold, K&n, Cat-back and lowerd 35mm.

 

Then they are wrong ...
I have had a similar problem on my parents Fiesta Zetec-S and it turned out to be the coilpack ... it ran poorly and misfired bad in the low RPM range but fine after 2500 rpms.
New CP on, and cured it right away.

 

Hmmm, I was also thinking a maf sensor, crank sensor or something only one way to find out. Think i am going to have to put my hand in my pocket first its going up for sale tomorow aswell why happen now lol

Thanks,

 

The ST's don't have a MAF sensor (as far as I know) ... crank sensor failure is very very rare ... so I would def say coil pack.

Good luck, mate ...