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Hi! So my roommate's Camry starts leaning out / raising LTFT as your acceleration progresses. Around +17% at 30mph and +24%ish by 45-50 mph. However, it just barely doesn't get high enough to trigger a lean engine code.
I've ruled out MAF by swapping the known good and compatible one from my car to hers. Trims didn't change at all after some driving. Her A/F sensor is brand new, and the post-cat O2 is 2 years old, both OEM.
So I'm kind of leaning towards a fuel pump that's weak. (There's no drivability issues)
However, my question is about the fuel trim characteristics of a weak fuel pump.
When I'm STATIONARY (not moving, and car warmed up) and revving the engine up to 3k RPM, the LTFT is the exact same as when it is idling (600-700rpm) (0-4% LTFT).
Should I be seeing the lean trims with the increased engine speed while stationary, if it was a weak fuel pump, or is actually DRIVING around the street the more indicative / required way of determining a fuel pump trim characteristic?
Short bursts will not effect fuel trim numbers much. When revving an engine to check for weak pump you will want a fuel pressure gauge installed on fuel line and take readings at idle, 1500, 2000, 2500 rpm. If fuel pressure drops at higher rpm it's a weak fuel pump. If fuel pressure is low and goes lower with increased rpm check fuel pressure regulator by doing a key on engine off test read initial fuel pressure and see if it drops quickly. It should if functioning correctly hold pressure for 10 minutes or more. If not it will drop rapidly within 10 minutes. This would cause lean at higher rpms.
