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Have a 2017 Subaru forester I'm taking over for another tech. Has p0171 lean code set. So he's been replacing parts, replaced maf sensor, a/f sensor and fuel pump. Nothing fixed. I looked over at my fuel trims at idle found short term fuel trim is at 22% long term 0 for the moment. Rev engine goes to 0 on short term and eventually long term goes 22% checked for vacuum leaks (smoke test) no leaks found I'm wondering if I'm having an injector issue. Any guide to the right direction will be gratefully appreciated
If fuel trims don't go closer to zero with rpms, I'd look toward fuel deliver too. Sometimes it's hard taking a job over because you don't know if their repairs could have caused another problem.
You can see if it's losing fuel by running WOT while monitoring the o2 sensors to see if the dip down at all. they should stay high the whole time.
If you suspect an injector issue you could try an injector balance test.
The Fuel Trims trims you describe are not indicative of a vacuum leak.
Prove the O2's respond to a rich condition by adding propane into the air stream. Check for exhaust leaks upstream of the o2 sensors(false Lean)
Verify Fuel Pressure matches what PCM is seeing, or Commanding at all engine ranges.
Can you post the ABS Load and Calc. Load , what are the values at idle in drive, and what are they at WOT on a test drive?
Can you post the engine in liter size and a MAF reading in grams/second ~4000 rpm under load?
You have Fuel Trim at all engine ranges, so either the Air is not being measured correctly, or there is a fuel problem. The above information will help determine which path to follow air or fuel.
So the engine is a 2.5 non turbo when I look at my 02, voltage is reading 7.2 volts. Injector pulse is reading 2.5 ms I'm not finding any exhaust leaks. At WOT I'm seeing my short term go from 22% to zero and long term is going to 25%
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