I have done alot of searching on this, but feel it will be easier to post the problem. Its a 97 F150, 108,xxx miles. The plugs and wires were replaced about 30-40k ago. The coil and o2 sensors are still the originals. Last weekend I pulled the middle plug on the driver's side to see if it still looked good. After I put it back in I started getting a miss. I put a different plug(Motorcraft 42FM gapped at .54) and different wire on (New Taylor Wire) and still have the miss. It does it under 2k usually, and only under heavy acceleration. It isn't throwing a code to cause a check engine light. I also have a problem with rough start.

Are these related? I have checked the forums and come up with these solutions:
Replace coil
Replace o2 sensors
clean IAC
clean MAF
clean TB

Anyone have any other suggestions? I hate to start replacing things without exhausting all my options beforehand. Also, I have an Airraid FIPK, which I have seen people saying will cause some problems, but it has 40k on it and has been on through a few computer resets.

 

Well, I took care of the misfire-one of the other plugs was bad. Still, Im trying to decide if I should replace the coil/o2 sensors. Will the benefits outweigh the costs of doing all that? I figure the sensors and coil will cost me around $300 and 2 hours of my time. Will replacing these help out gas mileage signifigantly?

 

If you fixed it, and it runs good...leave it alone. O2 sensors are 50 bucks a pop at autozone. I don't know about the coil. I'm sure replacing them will yield you a little better mpg's, but not much. If you have the $$$ and time, go for it.

 

My truck also started a bit rough a few days ago. It felt like it was missing. It went away with a couple revs of the throttle. New plugs and wires about 25K ago as well here. Did my best to get original plugs for it.

 

ive replaced my 02 sensors twice in 122k miles. once for 02 heater circuit problem ans once for slow response of 02 sensors. if they have never been replaced and you feel like doing it it shouldnt hurt anything. my mileage only went up about 1 mpg after i replaced them the last time. but 02 sensors could make gas milage real bad and still not trigger a light.