2001 Ford F150 " Service Engine Soon"


Old 12-22-07, 12:48 PM
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Join Date: Jun 2006
Posts: 20
Unhappy 2001 Ford F150 " Service Engine Soon"

The "Service Engine Soon" light came on in my dash and I took my truck in to see a mechanic. He pulled codes PO171 and PO174 saying that the fuel is too lean on bank 1 and 2. My truck is still driveable. The mechanic stated that I may have a "Head Gasket problem" or a " exhaust manifold problem." My manual says to check the gas cap and put a higher grade of fuel in. I did that and no change.

What could be the problem?
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Old 12-22-07, 06:14 PM
Join Date: Apr 2006
Location: Floriduhhhhh Us of A
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The vacuum lines in your truck are made of har plastic with rubber elbows to connect them where they gotta go.........Check the elbows..........specifically the ones leading from the PCV valve..........I'll bet the farm you're gonna find one has collapsed and is leaking
Old 12-22-07, 06:28 PM
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Join Date: Dec 2007
Location: RI
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I agree with wrench47, check the pcv tubing. What engine is in the truck? 4.6L and 5.4L have a lot of pcv tubing problems, especially right where it connects to the intake. The 4.2L has a lot of problems with intake gaskets.

I wouldn't go back to the guy who told you it may be a head gasket, I've been at a Ford dealer for 8 years now and have never seen a head gasket give a lean condition.
Old 12-22-07, 07:55 PM
Join Date: Aug 2003
Location: Cape Cod
Posts: 4,320
Originally Posted by Naauao2001 View Post
What could be the problem?
Not a head gasket...nor is it likely an exhaust manifold (though technically possible...just not likely)

More likely it is a vac. problem as mentioned
Those elbows can look fine, but underneath be cracked
You'll need to do a real good thorough inspection

Check for loose/cracked air inlet tubing too, that would do it

Also, I'd clean the MAF sensor
They get gummed up, and can cause this reading
Old 12-26-07, 03:43 PM
Thread Starter
Join Date: Jun 2006
Posts: 20
2001 Ford F 150 "Service Engine Soon"

I checked all the compression hoses and elbow to the PVC system and found no leaks. The PCV Valve has compression. I cleaned the MAF and still have the "Service Engine Soon" light on. Any other suggestions?
Old 12-26-07, 06:14 PM
Join Date: Aug 2003
Location: Cape Cod
Posts: 4,320
Even if you fixed the problem, it will take many on/off cycles for this code to clear itself on this OBD-II computer controlled engine.
The code must be cleared with a code scanner, or will take a few weeks to clear itself

Best to have is scanned/cleared so as not to have to wait and wonder
You should be able to at a DIY auto parts place
Many will do it for free or a small fee

(I can't recommend to go back the Head Gasket guy, sorry)

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