danweinheimer

I just changed the spark plugs on my 2007 F150XLT 5.4 liter. After everything was back together I started it and the emissions light was on and the engine was misfiring/ running very rough. I did some trouble shooting to make sure all of the plugs and coils were all good and they were. What else could it be?

allinon72

Double check that all of the plugs are torqued properly, not just tight. Get the code scanned to point you in the right direction. I would bet that you have a bad coil that went bad at the same time coincidentally.

danweinheimer

Thanks for reply. its not a coil. I went and bought a new one. went through each cylinder and put the old plug back in and new coil on to make sure it was not either. never thought changing plugs would be such an issue

kitchenboy

Did you change the coil boots too. If not you should. Are you sure anything else you disconnected to get the plugs out is all back right.

Search

That was an insane amount of work.

Think smaller for a second. Any chance you unplugged anything with the fuel system and didn't replace? Any chance a COP wire is damaged and shorting out? Just small things.

What gets me is I've never heard of anyone's emission light coming on when having plug/coil issues. Get that thing on a code reader.

one1

Did you unplug the airbox and move it out of the way? If so did you plug everything back up like the vac line to the intake tube and the maf plug, etc....... Have you checked to make sure you didn't knock an injector plug off? It's something simple.......

Tradesman

I would start from the beginning and check every single component you touched.

danweinheimer

taking it to a shop to see what codes come up later today..will post results

techrep

iTrader: (1)

Did you apply dielectric grease to the COP's when installing ?

danweinheimer

sooo... took it to the shop and got the codes read. had a misfire code for almost every cylinder (they said most likely because the plugs were so bad and they would mis fire now and then and that they were old codes just not cleared because I didn't disconnect the battery) hooked it up to the snap on diagnostic tool and said there was a miss fire on cylinder 4(only cylinder I did not troubleshoot with an old plug because its the worst one to get to), they recommended I change the coil because of the location of this coil is right underneath a coolant line and is a common bad coil. I went home, changed it...still miss firing....so I swapped the new plug with an old one again and of course it worked.. turns out 2 of the 8 plugs I bought from advanced auto were bad. I think ill spend the extra money on motorcraft parts now. Half my fault I guess