Expedition Problems
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New User
Joined: Jun 2011
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Expedition Problems
My 99 Expedition is flashing PO 171 174 and 430. I have checked PCV elbow and intake gaskets and there are no noticeable vacuum leaks. what gives. I dont want to change out 02 sensors for no reason and the thing runs really well. I have cleaned the mass air sensor and keep on getting these codes. My smog check is coming up and i know that it wont pass with the light on. Thanks in advance for any and all advise.
Logistics Pro
Joined: Jan 2001
Posts: 3,740
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From: Central NYS
A vacuum leak a-n-y-w-h-e-r-e in the intake can cause the dreaded P0171/174. It doesn't have to be the famous PCV elbow.
It could be a pin hole leak in the intake path between the MAF and the throttle body.
Is your dipstick fully seated?
I found my P0174 problem was the return line for the PCV replacement air was not fully seated in the valve cover.
Also, check the famous "battery acid eats the vacuum hose" behind/under the battery tray.
The P0430 might just be a by-product of the P0171/174.
It could be a pin hole leak in the intake path between the MAF and the throttle body.
Is your dipstick fully seated?
I found my P0174 problem was the return line for the PCV replacement air was not fully seated in the valve cover.
Also, check the famous "battery acid eats the vacuum hose" behind/under the battery tray.
The P0430 might just be a by-product of the P0171/174.
Fleet Owner
Joined: Apr 2008
Posts: 24,322
Likes: 5,132
From: 0,0,1
You can get all of these codes when your fuel pressure is low, such as when the fuel filter is plugged, or the fuel pump is starting to go bad.
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JoeG112
1997 - 2006 Expedition & Navigator
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Nov 13, 2011 09:27 AM
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