rjstubbl

I have a 2005 F150 STX with the 4.2 V6 (manual trans). Recently the motor started to stutter (misfire) under light acceleration. I replaced the plugs/wires and now the problem is worse and it stutters through all the gears.

Could it be a bad coil or fuel injector?

The check engine light came on and P0306 and P0316 codes came up.

Thanks for the help.

nrivera04

Coil seems to be a popular failing item with the v6 engine. It'd be a good start. Other things could be a bad plug or plug wire.

techrep

iTrader: (1)

Replace the COP on cylinder #6

2008__XL

4.2 doesn't use COPs. It uses plug wires.

BadFish523

P0306 indicates a misfire on cylinder 6. Check the connections out very well on that cylinder.

techrep

iTrader: (1)

Bad plug or plug wire.. you can swap injectors to troubleshoot

rjstubbl

So I changed the coil and that didn't help. Bought a new spark plug, put it in #6 and that did the trick. I realized when I was installing them the first time, the #6 plug slipped out of my hand onto the concrete floor...maybe this cracked the ceramic? But anyway, running good now with a new new plug in #6.

Thanks for the help.

nrivera04

Good theory. Any time I drop a plug, I write it off. It is even possible to get them bad out of the box. Glad you got it fixed up and thanks for reporting back!

techrep

iTrader: (1)

That will do it..