1997 - 2003 F-150

Error Codes

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Old Dec 14, 2014 | 08:39 PM
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Error Codes

My wife and I received her father's 2002 F150 4.2 5 speed 2 wheel drive truck after his passing. He purchased new plug wires and wanted to replace them. So, this weekend I put in new plugs, plug wires, changed the air filter, and changed the oil and filter. Started up and ran really rough. Threw my code reader on after taking it around the block and found the following codes...
P0316 Misfire detected in first 1000 revs, P0302 Cylinder 2 misfire, P0305 Cylinder 5 misfire, P0306 Cylinder 6 misfire. New plugs were Motorcraft plugs, but had skinnier center compared to the ones that came out of truck.

Where do I start? What do I do? I am really confused as I have changed plugs and wires before and always had vehicle run better or same as before change.

Any thoughts and advice is welcome.
 
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Old Dec 14, 2014 | 09:35 PM
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From: Joplin MO
It's easy to cross wires at the coil - verify your firing order. Hope you used Motorcraft wires and dielectric grease.
 
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Old Dec 15, 2014 | 06:50 AM
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I used Motorcraft wires, and plugs (was told that these trucks are picky that way). Replaced plug wires in proper sequence followed firing order which I had printed out and had with me as I did the work. The wires appeared to have dielectric grease in them so I did not use any extra. Not using any dielectric grease does not explain the codes being thrown, especially for cylinder 2, 5 and 6 if the code did not come up for 1,3,4.
 
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Old Dec 15, 2014 | 06:09 PM
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You need sp504 MC plugs. If that isn't what you have replace them again. you can get them from rockauto.com
 
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Old Dec 16, 2014 | 01:16 AM
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I'm not positive but I think there are 2 different firing orders for the v-6. You may have the wrong one.

I have also had bad plugs out of the box. So 2 wires switched and 1 bad plug and there are your 3 cylinders with misfires.
 
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Old Dec 16, 2014 | 06:52 AM
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I do have the SP504 plugs. Not sure about having bad ones. Only firing order I have seen for the 4.2 V6 on the coil is (front to back) 123, 465. and on the engine it was (front to back) 123, 456. If there is a different firing order, I was not able to find it and would be interested to know about it.
 
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Old Dec 16, 2014 | 12:55 PM
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What you listed is the cylinder location counting order and coil terminals left side front to back 1,2,3,,,, coil right row front to rear 4,5,6..
The actual Fire order is 1-4-2-5-3-6 as the motor runs.
The coil windings are paired to two cylinders each. Three coils runs six cylinders.
The selected cylinder's plug is fired on it's compression stroke. It's mate also sees coil's voltage but during that cylinder's exhaust cycle when the spark gap looks like a near short to the high voltage and has no effect.
Actually with an ignition of this type the original spark plugs were 3 of one part number and 3 of another part number.
The reason is the polarity on 3 plugs is negative and 3 are positive. This actually affects the erosion rate of the tip material so the plugs for 3 cylinders were made from different metal composition.
For most practical purposes it makes little difference if the plugs are changed often enough.
Double check the plug leads.
If you did not do anything else, there has to be a mistake.
Good luck.
 
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Old Dec 16, 2014 | 01:01 PM
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From: Joplin MO
Actually with an ignition of this type the original spark plugs were 3 of one part number and 3 of another part number.
The reason is the polarity on 3 plugs is negative and 3 are positive. This actually affects the erosion rate of the tip material so the plugs for 3 cylinders were made from different metal composition.
For most practical purposes it makes little difference if the plugs are changed often enough.
Or you can use double platinum plugs, if available. SP504's are single platinum.
 
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