M4Florian
Ford SMAX Diesel Engine Running Lean
Summary of the thread
A 2020 Ford SMAX diesel is experiencing symptoms of running lean, including reduced power, a check engine light, and rough running with jerking during acceleration. A faulty injection valve is suspected as the cause. Suggestions include checking for carbon buildup in the intake manifold and EGR valve, but ultimately, a defective fuel injector is identified as the issue. Replacing the faulty injector resolves the problem, restoring the vehicle's performance.
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4 comment(s)
M4Florian (community.author)
No recent work, and I always use premium diesel. I don't have the exact error code, unfortunately. Carbon buildup... is that a big job to check?
stefan_friedrich5
Carbon buildup, while not ideal, is a common problem on modern diesels. However, based on your symptoms, a defective fuel injector is indeed a strong possibility and fits your vehicle's mileage. Without the error code, it's hard to be definitive. I would advise taking your SMAX to a qualified workshop for diagnosis before you start tearing things apart.
M4Florian (community.author)
Thanks a lot for your input! Took it to the shop, and you were spot on – faulty injector! Cost me 515€ to replace. Runs like new again.
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FORD
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SMAX
stefan_friedrich5
Interesting. A lean condition on a modern diesel like yours could stem from several issues. Has the car had any recent work? Are you using quality fuel? Do you know what the error code is? It might be worth checking the intake manifold and EGR valve for any carbon buildup.