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Engine misfiring whilst on boost

FrankieDibble
FrankieDibble
in Ford Fiesta Club

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Hi all, I've been browsing this site on and off since owning my ST and thought I'd sign up and ask for some advice if I may. 

I have a 2015 ST3 with 78k miles on the clock. I’ve owned the car for 18 months and in that time have had no running issues. For the past 6 months it’s been running a Pumaspeed Stage 2R map with no issue. I changed the plugs roughly 3 months ago and again no issue and the car has been running great until today. Now when I put my foot down it pulls as normal until I get to around 10 psi of boost. It then sputters and misfires non stop until I ease off. The car appears to drive fine if I keep out of boost. I can still gradually accelerate up to speed as if all is fine. I plugged forscan in and mode 6 shows misfires in cylinder 2. I swapped coil pack 2 with cylinder 4 and tested it hoping cylinder 4 would now be misfiring and therefore point to a defective coil pack. No such luck though, it still misfiring on cylinder 2. Forscan shows no DTC fault codes and I have no check engine light on the dash either.

Could this be a faulty injector I’m looking at here or is there something else I’m missing? Also I need the car for work all week, would it be ok to drive off boost during this time without causing further potential problems?

 

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