Po 174 on a 2003 expedition 5.4 engine - 2003 Ford Expedition

the ignition coil on cylinder number 5 secondary circuit malfuncion

This is a tough one could be mass air flow sensor ,oxyegen sensors,a fuel filter. a vacum leak, a pcv valve if i missed anything just google po 171 &174 look for fix ya this issue has been addressed many times first check the vacum lines includeing the line on the pcv valve for cracks or splits in the lines .I would do the fuel filter if it hasnt been changed in the last couple of years , if still a problem the MAF sensor if your happy with my advise please leave me with great feedback

The code is for a problem with the ignition coil for cylinder number 5.

my engine light also came on one day and I got the same, its common in older cars for this light to stay on all the time, you can truble shoot this by spending money on each of the engine sinsors, but i have had this light on for over 5 years and nothing is wrong with my car

For 2003 Ford Expedition there are 4 different engines:
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For Expedition 4.6L engines: Firing Order 1-3-7-2-6-5-4-8



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For Frod Expedition 5.4L engines:

Firing order 1-3-7-2-6-5-4-8





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Ford Expedition 4.0L engines:

Firing order 1-4-2-5-3-6 ---



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For Ford Expedition 6.8L engines:

Firing Order: 1-6-5-10-2-7-3-8-4-9

PO -133 O2 Sensor Slow Response

Po -- 153 same thing


Check for vacuum leaks --every where

Clean MAF Sensor -CRC MAF Cleaner

Replace the 2 --front O2 Sensors, if over
100,000 miles on them The ones closest to motor

Use the OEM Type not the cut & splice
universal junk

NAPA can order them
Should be Bosch or NGK

Codes do not tell you anything about what is wrong
or what to replace.

Code--PO 307 ?

Try changing that COP Ignition Coil

50/50 you'll get it right

Replace the #5 COP Ignition Coil
About $60.00 at the auto parts store
Front coil,drivers side.

Disregard the PO 300, also PO 171 O2 Sensor, get ride of misfire on 5 ,and see if you still get codes.
Clear Codes after you do coil.

Please do not go to a dealer
You will leave a couple grand there, and still have nothing fixed

It sounds like the convertor in the exhaust system is partly blocked. You will need to have this checked at a shop. Frankster016