Long term and short term fuel trims intake leak, low idle, improving fuel mileage. Mpg

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Did you reset the LTFTs when the injectors were replaced? Those values are learned and could be carried over from the prior situation. Eventually they should get closer to what the STFTs run.

The STFTs show it slightly adding some fuel, well within ideal, so there's that. Those are instantaneous trims, and reset at every ignition cycle.
 
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Burban22

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Did you reset the LTFTs when the injectors were replaced? Those values are learned and could be carried over from the prior situation. Eventually they should get closer to what the STFTs run.

The STFTs show it slightly adding some fuel, well within ideal, so there's that. Those are instantaneous trims, and reset at every ignition cycle.
I don’t have a nice enough scanner to reset LTFT. I disconnect battery for a few days which I thought reset the LTFT? If not hopefully it will get better after 100 miles or so.
 
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Burban22

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I’ve only put on 100 miles since injectors were cleaned and LTFT are still -7 to - 12 at idle but during driving my STFT are now adding fuel occasionally along with the LTFT. This is a change for the good as before injector cleaning it was almost always removing fuel at idle and driving.

I’ll post back my next few hundred mile highway trip if any mpg improvement but I’m doubtful as I could still pull down 16 - 17 at 65 with dirty injectors.
 
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Burban22

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Holy crap that fuel injector cleaning service really helps!

We got 22 miles to the gallon down to Phoenix and back up to mayor / Arcosanti.

15mpg on the climb from Arcosanti to NAZ. Best I could ever get before was 18 - 19 down and 13-14 up.

Fuel trims are still negative at idle but while driving on the interstate 68-70:
STFT -5 to +6
LTFT -7.8 to +6
 
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2006Tahoe2WD

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Received my cleaned fuel injectors back with new upper and lower O-rings although I had to replace the lowers with the originals as the O-ring they included were just a little bit too big and I couldn’t get the injector all the way in the intake.

The place I used only charges $9-$10 per injector after shipping so they don’t include flow rates.

My injectors do look much cleaner and they replaced the screens inside the injectors and the lower plastic caps.

After all this, my fuel trims are now taking away even more fuel, -12.5 at idle but -3.5 to -9.5 driving. I’ve only driven it once since resetting the computer as the battery was unhooked for a few days.

Suburban runs the same. Will see if there’s any fuel mileage improvement, but I would assume the injectors were dirty after 170 K miles and 20 years.


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Good info. Thanks for the report.
 

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