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SuperBob, Ford Senior Master, Mazda Senior
Category: Ford
Satisfied Customers: 2609
Experience:  18 years Ford, Lincoln, Mercury, Mazda Dealer ASE master, diesel certified. Specialize electrical
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2003 Expedition 5.4l P0174, System too lean Bank 2 Good idle

Resolved Question:

2003 Expedition 5.4l
P0174, System too lean Bank 2
Good idle and misses under load.
Fuel filter good
Submitted: 5 years ago.
Category: Ford
Expert:  SuperBob replied 5 years ago.
I suspect that one of your coils or spark plugs on the drivers side of the engine is not contributing as well as the others! If you do not have a complete spark, you will have one part of fuel to about 15 parts of air go down the tailpipe and then the oxygen sensor will indicate a lean condition! I would advise that you disconnect one coil at a time on the drivers side of the engine and drive the vehicle to see if the miss fire is drastically worse! Road test it, then if by unplugging that coil did make the engine run worse under the same driving condition, plug the coil back in and move on to the next coil and repeat! Once you get to one of the coils that DOES NOT make the engine run worse, I would swap out that coil with one of the previous ones that you tested and repeat the test! I suspect that you have a failing coil, and if the problem follows the coil, you will need to replace that coil! If the problem stays on the same cylinder, replace the spark plug! Coils cost about 90 to 100 each!
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