r/FocusST • u/Ok_Buy_5315 • 18h ago

👋 HI, I'M NEW! I need help bad running lean

My focus st is running lean and dumps extra fuel to compensate for it. when i start the car the rpms are low and drop until the car almost stalls and then shoots up to 1500 then hunts for idle for a bit before settling and i have a rough idle. Now in pretty sure ive been fighting a vacuum leak but i cant find it for the love of god. On idle my stft is 0 but my ltft is 15 when i rev the engine to 2k rpm and leave it there the stft goes up to 18 and ltft stays at 15. Ive replaced my purge valve both fuel sensors upstream o2 injectors coils and sparks.

3 Upvotes

81% Upvoted

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1

u/BakaGG 16h ago

Im riding on this too...some said clean the intake manifold.

2

u/SCL36 Mountune N1 2.3 Stroker, G30-770, Xclutch, Tuned by Alan 16h ago

Try a throttle body reset maybe? Double check hose clamps and maybe do a smoke test for any possible air leaks?