99 4.6L missing and rough idle HELP!!

[Porkchop]

The 99 doesn't have the coil on cylinder set-up. Everytime I have this problem I have my brother-in-law, who is an ASE certified mechanic, pull the codes and sure enough it shows a misfire on some cylinder or another. You can pull that plug wire and sure enough there is oil on the cylinder. Seen it myself and helped in the repairs each time. You can clearly see the arc trace up up the plug and around the end of the plug wires boot. Once that happens, it's best to just replace the plug because once it starts a path, it'll continue because electricity takes the path of least resistance.

I replaced 7 of the eight plugs and all 8 wires at one time. The back plug on the passenger side was too hard to get out without an air rachet. I had to put brakes on so when I was in his shop we then changed that plug. Of course it was skipping real bad so I had planned the change anyway.

The best fix for this problem, if this is one you may be experiencing is to first find the oil leak. Stop that first. Then replace all eight plugs and then all eight wires. Clean the area where the plug wire pushes down around the top of the head. Use silicone to seal the plug wire boot to the cylinder, this will stop oil from getting into the hole again and hopefully stop this problem. It seems to be a common problem and a reoccuring problem.

 

[andyhaas]

I have a 99 4.6L and it is doing the same thing. I took it to a mechanic and he replaced the wires (I don't think they're motorcraft). It started back up and I took it to the dealer. A $175 sparkplug later (#2) and it was running much better. They didn't say anything about oil. It is slowly coming back. Do I need all 8 new plugs and a new set of Motorcraft wires?

My driveway is dry. Shoud I be seeing an oil leak?

 

[croatone]

you most likely have a bad coil pack.