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Old 07-16-2017, 09:10 PM
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wife was driving her 2002 expedition with 4.6l and it started running rough with back fire and no power. It finally went dead as she coasted into parking lot. Had it towed home. When i got home , I pulled codes p1450,p0171 and p0174. The p1450 has been there off and on but i have never been able to isolate problem. could p1450 be connected to the lean codes as well. Some of the freeze frame data was as follows:
ect 185
calc load 59%
stft b1 35%
ltft b1 25%
stft b2 35%
ltft b2 24%

upon checking fuel pressure, i had to cycle ignition 3 or 4 times to get pressure to 38psi, pressure drops to 30 with engine running. when i snap accelerator pressure goes up 6 or 7 psi. when i unplug vacuum line at regulator pressure rises 8 psi.
Having said all of this, it will start now and I cant get symptoms to repeat. Based on info, does anyone have any likely solutions?

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Old 07-16-2017, 09:19 PM
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Check for vacuum leaks. The PCV elbow behind the throttle body is a prime failure item.

Your P1450 is "Unable to Bleed Up Bleed Fuel Tank Vacuum".

Possible causes

Blocked EVAP canister or vent solenoid
Kinked or collasped hose between canister and fuel tank
Faulty Fuel Tank Pressure (FTP) sensor
Fuel filler cap stuck closed, preventing vacuum relief

I'd also change the fuel filter.
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Old 07-16-2017, 09:52 PM
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pcv elbow and hose was the first thing i checked, I'm thinking fuel delivery but cant get symptoms to reappear
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Old 07-16-2017, 09:56 PM
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fuel trims are normal at idle and rise on acceleration , i thought that if a vacuum leak was present fuel trim values would be high at idle and come down under acceleration
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Old 07-16-2017, 10:49 PM
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The 1450 code may be the hint that a vacuum in the fuel tank makes it hard for the fuel pump to pump fuel in sufficient volume.
If that happens the fuel trim tables will shift rich trying to correct the problem of lean fuel supply.
Since there may be a hard time pumping fuel, the richened tables just add to it make it worse and affect drivability.
That's one scenario.
It maybe that there are two different issues at the same time.
You need to look at it both ways.
The illustrate a simple example, on a lawn mower if the gas cap hole is blocked it will stall the motor in a minute or so because the fuel cannot be pumped against the vacuum that builds in the fuel tank.
Good luck.
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