97 F150 4.6L 203M miles. I had a miss fire so I replaced the plugs and wires.
number one had antifreeze around the boot causing the plug to short to the block, could here it in the radio, but not leaking now. Autozone meter said the front Oxygen sensor
was running cold. After the tune up all went excellent. Couldn't even tell the engine was running at a light. 18 days later it started to miss badly, autozone meter said misfire # 6, so I replaced the plug but it looked fine. I have spark, I tried unplugging the injector and that maid it worse. My question is could my Oxygen sensor cause me to have such a terrible miss ? and should I replace it ? Could my coil be weak to one plug ? Thanks Guys, sorry for the long question

 

203 million miles!

 

Prob bad coil pack. If the plug is new and still misfiring, change the pack. O2 sensor will make it run crappy but you will be able to tell the difference in o2 sensor crappy and bad misfire from bad coil pack.

 

Sorry, In my business M mean a thousand in the pricing of footage of wire or pipe. I have a used coil pack that I removed once before when I had a misfire
which turned out to be a bad plug wire by motorcraft. The used coil pack is fine and I'll try that tomorrow on the side that has that plug number first. I did have spark
to number 6 but may be just "not hot enough" Doesn't seem to me either that
a sensor could cause that much shake. I feel it most when under a slight load. Like I said the day before it run really smooth with plenty of power for an old girl. Thanks for your input, and I will post what I find

 

The O2 sensors are the primary input for the air/fuel ratio until above ~1/2 throttle. I replace mine at 40k miles with Motorcraft only.

By the way M works for me re: 1,000.

 

Changed the coil that covers the plug #6 that autozone said was misfiring, changed the plug, and put back on a old plug wire, and then put in a new oxygen front sensor on that side (passenger side) still running badly, but seems just a little better.
Disconnected the battery while working on the motor, so now I'm waiting for
the engine light to start flashing before taking to a different autozone to get a reading. I just know it's electrical by the way she acts. Any more thoughts out there ?
Thanks,
Dale

 

Changed the oxygen sensor that autozone said was running cold, ran a little better. Ran it on the express and continued to run just a little better. Thounght it might be fuel, so added a can of SEA Foam, what a difference in no time. So then decided to change the fuel filter which was original at 203,000 mile. Runs great, must of been a fuel delivery problem after all.