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John Mc
John Mc, Ford Technician
Category: Ford
Satisfied Customers: 6240
Experience:  19 years Ford Lincoln Mercury experience
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2003 Ford Expedition: p0171..4 o2 sensors..My Truck idles too slow

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2003 Ford Expedition, OBII codes obtained are P0171,System too lean Bank1,P0174 System to lean Bank2. I have replaced all 4 O2 sensors, and I Still get these 2 codes
P2195 and P2197. My Truck idles too slow and falls dead. Do you have any input on what the problem could be
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John Mc :

Hi, I am John Mc, a Ford dealer technician.
I hope I can help solve your problem quickly and accurately.

Please wait a moment while I work on your problem.

John Mc :

It sounds like you have a vacuum leak. This was probably your issue all along. Find the pcv valve in the passenger side valve cover and follow the vacuum line to where in goes to the intake. The elbow that connects to the intake is bad about rotting out and causing your whole problem. If this is the case go buy a new pcv tube from a dealer and you should be set.

John Mc :

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John Mc

If you still have follow ups please ask and I will be glad to assist.


No, thats not it I have checked the PCV Valve and its connecting elbow, no leaks detected.

John Mc :

Ok then, my next suggestion would be to remove your maf sensor and use some carb cleaner or brake cleaner to clean out the internal electrical part throughly. Take the battery loose while doing this so it can recalibrate the sensor when reconnected. You may just have a bad reading on your maf sensor causing the whole problem.

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