My truck just got it 1992 f150 5.0 and number 4 sparkplug wire is not there should it be there what is it for?
your truck should be good old simple electrics, the "wire" is actually what we call HT leads, High Tension leads carry the electricity from the distributor unit to the sparking plug, with a big old v8 you will probably not notice it but if you fit a replacement then the motor will run smoother and fuel economy will increase with better performance, given the age of the truck I would consider a new set of HT leads, new plugs and an oil change to finish off, should run like new then, prevent any unnecessary malfunctioning.
Replace all the plug wires. Do them one at a time so you don't get them mixed up. I would be real curious as to why it is missing a plug wire. Perhaps it was bad or maybe there is a problem with the #4 cylinder.
Running on 7 cylinders! If you think it runs fine on 7 wait until you see how it runs on 8! Like bob said get a new set of plug wires.
Looking for a Used F-150 in your area?
CarGurus has 195,039 nationwide F-150 listings starting at $290.
Search Ford F-150 Questions
Ford F-150 Experts