4.2 cutting out during acceleration
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Cross-Country
Joined: Dec 2019
Posts: 93
Likes: 0
4.2 cutting out during acceleration
First of all here whats been done,
back in october I replaced all 4 cats
all intake/induction system gaskets
cleaned all fuel injectors, orings
new coil
MAF sensor (replaced again 1 week ago)
spark plugs
fuel pump
fuel filter twice
fuel regulator, it ran great since then until a couple weeks ago and will cut out after you shift gears, especially after 4th and 5th, its worse w a/c on and a load in the bed, the engine runs smooth at idle and higher RPM, have checked fuel pressure and did a road test w gauge connected and never dropped below 30 lbs, listened w stethoscope to injectors and all hitting, checked plugs, does anyone have any experience with this problem? Forgive if I don't get right back to you I'm in and out of the garage its over a hundred deg in Texas! thanks
back in october I replaced all 4 cats
all intake/induction system gaskets
cleaned all fuel injectors, orings
new coil
MAF sensor (replaced again 1 week ago)
spark plugs
fuel pump
fuel filter twice
fuel regulator, it ran great since then until a couple weeks ago and will cut out after you shift gears, especially after 4th and 5th, its worse w a/c on and a load in the bed, the engine runs smooth at idle and higher RPM, have checked fuel pressure and did a road test w gauge connected and never dropped below 30 lbs, listened w stethoscope to injectors and all hitting, checked plugs, does anyone have any experience with this problem? Forgive if I don't get right back to you I'm in and out of the garage its over a hundred deg in Texas! thanks
Cross-Country
Joined: Jul 2016
Posts: 91
Likes: 0
Ran my code checker on it and it came up with a code 171 lean on left Bank after I shift into fourth it begins to cut out when I try to accelerate and then smooth out as it gains RPM then when I shift in the fifth it does the same thing again it only does it under lower RPM in higher gears and worse if the AC is on or have a bit of a load in the bed
More Turbo
Joined: Sep 2017
Posts: 574
Likes: 146
...code 171 lean on left bank...
You should also check the freeze frame data to determine engine parameters when code was set. Reporting them here will help us to understand the problem better.
Cross-Country
Joined: Jul 2016
Posts: 91
Likes: 0
I did a smoke test first thing, I did all the tests and replacements for this stupid code back in October, as said it worked great till a couple weeks ago- I’ll take it to a good shop and let them run scan…thank you for responding my friend
Mountain Pass
Joined: Apr 2017
Posts: 170
Likes: 9
You say that you changed all the intake gaskets, but did you replace the isolator bolts that hold the upper manifold to the lower manifold? The seals on the isolator bolts get old and weak and allow vacuum leaks.
Cross-Country
Joined: Jul 2016
Posts: 91
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Hotshot
Joined: Jul 2020
Posts: 10,469
Likes: 2,631
From: Near Salt Lake City
Double check the ignition secondary
Coil and plug wires
with the engine not too hot take a squirt bottle of water out at night and spray the spark plug wires and boots
Watch for lightning and replace the plug wires as necessary
Good luck
Coil and plug wires
with the engine not too hot take a squirt bottle of water out at night and spray the spark plug wires and boots
Watch for lightning and replace the plug wires as necessary
Good luck
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1st Gear
Joined: Mar 2024
Posts: 1
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Did you ever find out what was wrong?
I’m having a hell of a time trying to figure mine out sometimes it will run good for about 30 seconds then will start stalling out crazy whenever I hit the gas I have a p0603 code but I think that’s because I keep the battery unplugged due to ignition switch draining battery I need to take care of that as well
Fleet Mechanic
Joined: Jun 2023
Posts: 1,373
Likes: 382
From: WA
Is it a 4.2 with a 5 speed? Not much to guess on here.
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wizkee
2009 - 2014 F150
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Sep 4, 2018 01:00 PM