Fuel trim issue
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Senior User
Joined: Dec 2017
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From: Dalton, Ga
Fuel trim issue
I noticed my check engine light on the other day so I pulled the codes. P0171 and P0174 if I remember correctly...left and right bank lean. I cleared them and started watching my long term fuel trim. It was running much higher than it has in the past...always <1.1 and now in the 1.14-1.25 range. Changes that have been made recently are a new battery and swapping the K&N air filter out for a standard replacement. I also cleaned the MAF yesterday with no apparent change in readings. I haven't found any obvious air leaks. If it's an air leak, I think it'd have to be a small one.
Fuel trim is 1.00 when accelerating and <1.05 if there's any appreciable engine load...going up a hill is enough. At 60 mph on level ground, it runs around 1.15. At idle and in park, it's .095-.097. As soon as I put it in gear, it shoots up to 1.25. I realize this probably isn't a serious issue but we're headed out on an 1800 mile trip over Christmas with a 10k camper in tow, and I'm trying to make sure the Ex is ready because sitting on the side of the road with an angry wife, 3 kids, and 2 dogs is not my idea of a good time
Thoughts?
Fuel trim is 1.00 when accelerating and <1.05 if there's any appreciable engine load...going up a hill is enough. At 60 mph on level ground, it runs around 1.15. At idle and in park, it's .095-.097. As soon as I put it in gear, it shoots up to 1.25. I realize this probably isn't a serious issue but we're headed out on an 1800 mile trip over Christmas with a 10k camper in tow, and I'm trying to make sure the Ex is ready because sitting on the side of the road with an angry wife, 3 kids, and 2 dogs is not my idea of a good time
Thoughts?
FTE Leadership Emeritus
Joined: Sep 2003
Posts: 12,246
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From: Houston, Texas
You may want to check your PCV valve and make sure it's either not stuck open or dangling out of the valve cover. A guy with a 97 F250 with the 5.4 coulda swore he had worse issues. When I looked below the hood, his PCV valve was dangling loose.
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Senior User
Joined: Dec 2017
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From: Dalton, Ga
I expect the Livewire is displaying them as a decimal such that the low end expressed in my post would be -4% (0.96) and the high end +25% (1.25). I'll check the PCV and its associated connection. Seems odd that just dropping the trans in gear causes the fuel trim to swing from one extreme to the other.
Elder User
Joined: Jul 2012
Posts: 575
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From: Eastern KS
Not sure how the routing is done on the v10, but on the 5.4, where the pcv line connects to the back of the throttle body is known to crack and split.
Does the engine idle down when you drop into gear? Probably so, especially when cold, which closes the throttle plate or iac valve, which then it starts sucking air through the leak, which is bypassing the maf sensor. Then the fuel trims start adjusting to try to make the oxygen sensors happy...
Does the engine idle down when you drop into gear? Probably so, especially when cold, which closes the throttle plate or iac valve, which then it starts sucking air through the leak, which is bypassing the maf sensor. Then the fuel trims start adjusting to try to make the oxygen sensors happy...
Laughing Gas
Joined: Oct 2017
Posts: 1,143
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From: ND
Not sure how the routing is done on the v10, but on the 5.4, where the pcv line connects to the back of the throttle body is known to crack and split.
Does the engine idle down when you drop into gear? Probably so, especially when cold, which closes the throttle plate or iac valve, which then it starts sucking air through the leak, which is bypassing the maf sensor. Then the fuel trims start adjusting to try to make the oxygen sensors happy...
Does the engine idle down when you drop into gear? Probably so, especially when cold, which closes the throttle plate or iac valve, which then it starts sucking air through the leak, which is bypassing the maf sensor. Then the fuel trims start adjusting to try to make the oxygen sensors happy...
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Stanislaw
1997 - 2006 Expedition & Navigator
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May 25, 2015 10:53 AM
