po171 code only
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Tuned
Joined: Oct 2006
Posts: 411
Likes: 13
From: Great northwest
po171 code only
I have been searching and have not found an answer yet.
I have a 2003 expedition with the 4.6L.
It has a po171, bank 1 lean.
I hooked up torque pro, and the STFT seems ok, both are bouncing right around 0 a litte on each side.
LTFT on bank 1 is high, 25.8% on bank 2 it is around 2%
both front o2 sensors are low,
I did find a bad coil on plug #1, I moved it to the other side, but LTFT did not change. I do not know how long that will take if that is it. I will get a new coil on it tomorrow.
Am I missing anything? I did break 1 vacuum hose today while moving the coil, so I need to replace that tomorrow as well. This is one of the hoses that run to the steel tube on the back drivers side of the engine. Before that I got no changes from spraying carb cleaner.
Thanks
Sorry for the long post.
I have a 2003 expedition with the 4.6L.
It has a po171, bank 1 lean.
I hooked up torque pro, and the STFT seems ok, both are bouncing right around 0 a litte on each side.
LTFT on bank 1 is high, 25.8% on bank 2 it is around 2%
both front o2 sensors are low,
I did find a bad coil on plug #1, I moved it to the other side, but LTFT did not change. I do not know how long that will take if that is it. I will get a new coil on it tomorrow.
Am I missing anything? I did break 1 vacuum hose today while moving the coil, so I need to replace that tomorrow as well. This is one of the hoses that run to the steel tube on the back drivers side of the engine. Before that I got no changes from spraying carb cleaner.
Thanks
Sorry for the long post.
Fleet Mechanic
Joined: Feb 2011
Posts: 1,812
Likes: 88
From: Thousand Oaks, CA
I don't drive the car a lot, it runs great and have been fussing with this for a year.
After clearing yours when does it come back?
I have noticed that ours will only set the P0171 under specific conditions.
The engine must be hot, stop for 10-15 minutes, then startup and the code will get set about 1 1/2 min after startup almost every time. Less than 10 min with the engine off or more than 15 min and the code is not set. It's as if there is a test done by the computer at 1 1/2 min after startup. Open to closed loop switch over ??? I have replaced all the vacuum hoses, checked all vacuum accys, tightened bolts, sprayed carb cleaner, changed the bank 1 front O2 sensor with no change. It might be a small crack in the intake ??? Or maybe the heater circuit for the O2 sensor is not working ??? I just got torque pro so I'll get some data.
Fleet Mechanic
Joined: Feb 2011
Posts: 1,812
Likes: 88
From: Thousand Oaks, CA
I was thinking the problem was after the cylinders on the passenger side - cracked exhaust manifold, broken bolt, O2 sensors.
I had a slight exhaust tick and thought it was from a broken exhaust manifold bolt on the driver's side, but that would have set a P0174 instead of a P0171.
A vacuum leak before the cylinders such as at the intake would affect both sides of the engine and set both codes eventually.
While trying to repair the broken exhaust stud I checked the exhaust pipe to manifold bolts.
The driver's side was fine, but the passenger side bolts were about 3/4 turn loose.
The exhaust tick and the P0171 are gone.
I haven't removed the broken stud, yet, need another tool.
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