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Fiesta st2 mountune 215 reduced power, no boost

Cydop
Cydop
in Ford Fiesta Club

Featured Replies

Hi guys, so last week I bought a st-2 with mountune 215 installed on it, anyway, whenever I go past 4k revs I just completely loose boost and the car goes onto limp mode. Power is reduced by 25% and throughout all the gears their is no boost at all, before this problem happens I get boost fine in every gear but as soon as it’s goes into limp mode it cuts it all in every gear. When I turn engine off and on again everything work fine, I also get no faults on the dash,  has anyone had this issue or can help?

  • Quote


    If you only bought it last week first thought is get back to the seller.

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    • Like 1
    • Author

    I’ve contacted the seller and he’s getting back to me Monday, was just writing on this forum to see if their was a quick fix as I really want to keep the car, I’ve just check the fuse box under the bonnet and the engine cooling fan fuse is missing so I’m hoping that is the problem, but on the dash the car doesn’t show as overheating 

  • Quote
    52 minutes ago, Cydop said:

    I’ve contacted the seller and he’s getting back to me Monday, was just writing on this forum to see if their was a quick fix as I really want to keep the car, I’ve just check the fuse box under the bonnet and the engine cooling fan fuse is missing so I’m hoping that is the problem, but on the dash the car doesn’t show as overheating 

    Not all fuse positions are meant to be used, I think there are 3 possible positions for the cooling fan fuse.

    Did your car come with a plug in Mountune handset? Some 215 kits were DIY, this handset can also read fault codes, if you can read the codes that would help.

    Has the car got the mountune intake system or a different open filter kit on it?

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    • Like 2
    • Author

    Yeah so I’ve checked the fuse and we’re the engine cooling fan is supposed to go in the handbook their is no earth to connect anything too, it went in to mountune to get the kit so it didn’t come with the handset, but I did have a Bluetooth obd handset lying around and it’s showing no codes, the dealer I got the car from is getting back to me tomorrow so hopefully he can sort it 

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    Fair likelihood he won't find it easy. I think you should seek advice from Mountune who will probably have seen this before and know what to look for.

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    • Author

    Right lads, it’s all sorted now, turns out it was just a dodgy map sensor it’s running like a dream now 🥳

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    The "Digestive"

    • The Digestive Forum Roundup (24th May - 31st May 2026)

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      The Digestive Forum Roundup (24th May - 31st May 2026) We hope this email finds you well and enjoying your week. As always, our forum has been buzzing with activity, so we’ve compiled the highlights for you. Plenty of interesting discussions are taking place, especially around the Ford Focus and Fiesta models. Starting off with the Focus, many members have been discussing issues with the Emergency Call System, particularly in the Mk4 model. PLB raised concerns about persistent malfunctions, a se
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