5.4 Check Engine light only when towing
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Tuned
Joined: Jul 2002
Posts: 462
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From: Kansas City, Mo
5.4 Check Engine light only when towing
I have a 1998 Expedition, 5.4. 217,000 miles. I have changed the pcv valve and the lines to it, cleaned the mass air flow sensor. I get the lean on banks 1 and 2 when I tow my travel trailer. I can clear the codes and drive the truck for weeks with no codes. When I hook up the trailer within 5 miles the check engine light comes on. I have searched the forums and haven't been able to come up with anything. Anybody have any other ideas????
John
John
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Joined: Jul 2001
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From: South Kitsap County, WA
Battery draw? Just throwing that out there. Pulling the trailer doesn't do a thing to engine performance... the only thing I can think of that has changed is your electrical.
-Kerry
-Kerry
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Joined: Jan 2006
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How old are your 02 sensors?
Sometimes they slowly degrade, often not enough to throw a code under normal conditions but when puling you are at high engine load/large throttle openings.
I replace mine regularly, every 40K miles or so as preventive maintenance.
Sometimes they slowly degrade, often not enough to throw a code under normal conditions but when puling you are at high engine load/large throttle openings.
I replace mine regularly, every 40K miles or so as preventive maintenance.
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Tuned
Joined: Jul 2002
Posts: 462
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From: Kansas City, Mo
The O2 sensors after the cat were replaced about 20,000 miles ago. I haven't changed the front two because they look like a pain to get to. I guess I'll have to get them changed this weekend hopefully. Thanks for the replies. John
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Joined: Jul 2002
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From: Long Island USA
Clean the MAF - oh, wait you already did that 
When was the last time the fuel filter was changed?
When was the last time the fuel filter was changed?
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Tuned
Joined: Jul 2002
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From: Kansas City, Mo
I have never changed the fuel filter. How would a dirty fuel filter give a lean code? Thanks for the reply krewat. John
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From: Long Island USA
Originally Posted by shadows4
I have never changed the fuel filter. How would a dirty fuel filter give a lean code? Thanks for the reply krewat. John
My V10 sucks up a lot of gas, and by 20K miles, the fuel filter was pretty well clogged and certainly made a difference in regular driving. If you don't know it's been changed recently, do it.
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