Misfire on 5 and 6

Tiny
TOTALMC
  • MEMBER
  • 2005 TOYOTA 4RUNNER
  • V6
  • AUTOMATIC
  • 70,000 MILES
Running rough, misfire on 5 and 6

Put in new plugs, no change

Smoke test showed no vacuum leaks

Fuel pressure 44 psi, holds steady

Swapped coils and freshly cleaned injectors with another cylinder, misfire stayed on 5 and 6

Live data numbers look good, except LTFT
B1 +12, B2 -15, STFT look good

Not sure where to look next. Thanks for any ideas in advance
Friday, December 19th, 2025 AT 8:51 PM

2 Replies

Tiny
AL514
  • MECHANIC
  • 5,519 POSTS
Hello, with an fuel trims reading the opposite per bank, if the Oxygen sensors are operating correctly, I would do a back pressure test on both banks at the front oxygen sensor location. On a V engine that is having trouble breathing (taking in air and letting exhaust out), you can end up with fuel trim numbers like this. Actually there was a case study on a vehicle with these exact numbers and had a restricted exhaust on one side of the engine.
Seeing those numbers, that is the first thing that comes to mind. The engine is very unbalanced right now, with a lack of air flow on one bank, we get a PCM/ECM that starts to try compensating for one bad bank and it effects the other side in the process.
Have you ever done a back pressure test and is the air intake system stock?
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Saturday, December 20th, 2025 AT 12:10 PM
Tiny
AL514
  • MECHANIC
  • 5,519 POSTS
This is the video on a fuel trim balance issue from bank to bank. Great video.
https://www.youtube.com/watch?v=hmFozmTf7xg&t=35s

https://www.2carpros.com/articles/how-to-test-a-catalytic-converter

https://www.2carpros.com/articles/bad-catalytic-converter-symptoms
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Saturday, December 20th, 2025 AT 12:14 PM

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