Here is a little more of the back story:
When I bought the truck it was missing on #3; I know this because when I pulled the #3 wire the engine ran the same. All the other wires when pulled, caused a change. My concern at that time was that it had a dead cylinder, but I felt it was worth the risk and if need be I would do a compression test.
The first thing I did was check #3 for spark and found a fouled plug. I bought a plug and once installed the misfire was gone. The truck was firing on all 6 cylinders!
I took it for a drive around the block and let it run for 15min. Once it warmed up it seemed to be running descent (for a truck that obviously needs a tune-up). I turned it off while I worked on some other stuff and when I started it back up (cold) it was missing again. But this time #5 was missing. So I pulled the #5 plug, and it was caked up, but after I cleaned it up it had good spark. When I put it back into #5 it made no difference and #5 was still missing. I also switched wires and that made no difference. There seems to be spark on all 6 cylinders. This is why I did a compression test. (#5-190PSI/#3-165PSI) I needed to remove the plugs anyway.
The reason I suspect a clogged injector is because the plugs I pulled all had good spark. The wires had spark too. (They need replacing, but all seem to be functioning, so that makes me think its not missing because of spark). The compression test shows me that the misfire is not due to a compression issue (every cylinder should fire). Also the truck has been sitting for some time (6 months probable more) and the guy I bought it from told me he drained the gas and put a 1/4 tank of 91 octane in the truck. (Only a 1/4 tank and of gas that I think could be to rich) That doesn't seem like enough gas after that amount of time sitting. I plan to listen to the injectors when I re-start the truck if it still misfiring. Then I will know more, but was wondering was a possible or even common cause for a misfire.
*That reminds me I need to replace the fuel filter ASAP. Any recommendations on a good filter?
whiskeymike's post seems logical to me; start with the basics and work down the line gathering more evidence. Along with plugs(Motorcraft platinium) and wires; I think I will change the oil and replace the fuel and air filters. Then fill the truck up with regular and fire her up
Any recommendations on fluid choices? Additives?
Other things I should consider doing before the re-start? I was thinking of fogging the cylinders before I put the plugs in.
Any thoughts on that?
The air intake tube is leaking were it attaches to the throttle body. This causes a check engine light, but when pressed in and sealed the engine light goes away. Either way there is no change in how the engine runs sealed or unsealed.
I plan to fix this, but could that cause a steady misfire on one cylinder only?Should I be looking into an air intake problem?
Again thanks to all! I am grateful for the input.