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Short Term Fuel Trim and Long Term Fuel Trim both positive

  • normand1234
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17 Oct 2021 11:30 #52062 by normand1234
Hello All

I have a 2010 Honda CR-V (4 cylinder 2.4L engine) and I am having a lean code on the car, short term fuel trim is 25% on bank 1 and long term fuel trim is 35.2%.

I would like to know from you guys what I should test first. Vaccum Leaks or Fuel Pressure? (I don't have a fancy OBD2 that can give me the fuel pressure from the rail)


Let me know your thoughts.
Thanks

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  • Tyler
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17 Oct 2021 12:31 #52063 by Tyler
Thanks for providing the freeze frame data. B) Shouldn't need a fancy scan tool for this one - your C-reader will likely be just fine.

Given that the code set off idle while driving down the road, I wouldn't immediately suspect a vacuum leak. I can count on one hand the number of Honda/Acura vehicles I've seen with bad fuel pumps. ;) Doesn't mean it can't have a fuel pressure problem! It just isn't very high on my list of suspects.

I'd be more suspicious of a torn intake boot or debris on the MAF sensor. Both can be checked visually with a little disassembly.

If you're interested in learning some fuel trim diagnostics, I'd suggest watching engine speed, MAF g/s, MAP, short and long trims and Absolute Load. Do this while idling, driving down the road and during a WOT run from a stop into second gear. The trim behavior, MAF and Load readings will help you narrow your list of suspects.

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19 Oct 2021 09:14 #52122 by normand1234
Thanks Tyler. I will review this great suggestions and will try to find the problem.

I do appreciate your input and I will keep in mind to come back and post what I find.

Thanks and have a good day.

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