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Old 10-19-2023, 11:24 AM
racebmwm3 racebmwm3 is offline
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P0171 P0174 Check Engine Light CEL

INTRO:
Month ago I got a CEL for these codes ago. Reset the codes to see if they would come back.
They came back just recently so I added a bottle of Red Line S-1 to my full tank and drove it. The CEL came back on again after some time.
Now every time I reset the CEL light, it comes back on after 20 mins of driving.

DIAG:
Checked the intake boot etc for leaks, didn't find any.
Checked for leaks around the DISA (mine is fairly new) - none.
Checked for leaks around the intake gasket, didn't find any.
Checked for leaks at fuel filter, found a cracked vent hose. Replaced. Still throwing CEL.
CCV is fairly new, within last couple years.
Pulled oil cap, engine gets rough (as expected)

FUEL PRESSURE: ***
Fuel pressure at running idle - 55 psi (ABOVE max spec of 46.4)
Fuel pressure, jumped pump (car not running) - 54 psi (at max spec)
Fuel pressure drop after 20 mins shut down - 4 psi drop (within spec)

I got a lotta miles - 255k. Not sure I ever replaced the fuel filter. Might be the culprit. Do we agree? Or could there be something else causing the high fuel pressure? Or is this high fuel pressure in response to the lean condition?


***
10/31 - I got a new fuel pressure gauge: The new gauge is reading the following:

Fuel pressure at running idle - 49 psi (ABOVE max spec of 46.4)
Fuel pressure, jumped pump (car not running) - 49 psi
__________________
2005 X5 3.0 6-spd.

Last edited by racebmwm3; 10-31-2023 at 05:27 PM.
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