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Old 12-10-2014, 08:44 PM   #1
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Default 1998 4.6 bad backfire!

I recently got a 1998 F150 4x4 with the 4.6 v8 in it. It has 212000 miles on it, and came up with a code for misfire on cylinder #3. The sparkplugs looked kinda old so I figured that they may be the problem. I put in new autolite plugs and wires and gapped them to .054. Now I have bad backfire under acceleration and it runs rough. I Have checked everything, the connections are in the right order. They all seem to be firing fine too. I checked the injectors with a screwdriver and they all seem fine. I have poured multible engine cleaners down the throttle body and they haven't fixed the problem either It ran fine before I did all this, so I'm very confused on what it could be. Does anyone have any idea what this problem could be?
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Old 12-10-2014, 09:05 PM   #2
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First of all change your plugs to motorcraft. May not be the root of your problem now but will save you trouble down the road. Double check your plug wires.
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Old 12-11-2014, 04:17 AM   #3
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Right, - use OEM plugs. Autolites can't always handle the heat range. - Aren't manufactured to Ford spec
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Old 12-11-2014, 07:23 AM   #4
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Cross any plug wires?
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Old 12-11-2014, 02:41 PM   #5
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X3 on the plugs... don't use anything other than Motorcraft... change em out torque them correctly and check all of your wires and connections... might just fix the problem... thing went from missing to running terribly... you did something wrong...
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Old 12-12-2014, 07:15 PM   #6
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Ok thanks, Autolite is what was already in the truck. All the wires are good and not crossed. Any possibility it could be the ignitions coils?
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Old 12-12-2014, 07:46 PM   #7
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Did you take the autolites out and replace with motorcrafts?
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