Bad misfires on cylinder 6 (P0306 & P0131 o2 sensor low voltage b1 s1)?

2012 FORD F-150
197,000 MILES • 3.5L • TURBO • AUTOMATIC
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REGGINA
  • MEMBER
  • 8 POSTS
Driving home from work last night I started to misfire on cylinder 6. I swapped a good coil and put a new plug in, still the same. Its a very bad misfire under very little load, have to slowly accelerate. Truck shakes, however the misfires aren't as bad at lower speeds (0-40). I recorded some live data and when I try to apply gas my absolute load value will go over 100% under normal operation.

I have noticed a rougher idle at start up over the last few months and a slight tick
Sep 24, 2026 at 2:30 PM
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REGGINA
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  • 8 POSTS
I assume I should check compression?
Sep 24, 2026 at 2:55 PM
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STRAILER
  • ✓Experienced Mechanic
  • 55,540 POSTS
Yes, that is a good start, also please upload a short video of the engine idling, this will help. Here is a video to help with the compression test. Also it could be a fuel injector that is not working FYI.

https://www.youtube.com/watch?v=KOxIm1F8AW0&pp=0gcJCS8MAYcqIYzv

Here is a misfire guide I would go over as well.

https://2carpros.com/articles/engine-misfires-or-runs-rough/

Since you've noticed a rougher startup for months along with a tick, I'd listen carefully around the #6 valve-cover area and the high-pressure fuel system. EcoBoost direct injectors and the high-pressure pump naturally make considerable ticking, but a new or unusually sharp valvetrain tick combined with a dead cylinder deserves a compression/leak-down test.
Sep 25, 2026 at 6:14 PM
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