have a 2003 F150 5.4 with 103,000 miles on it . The other day I thought I would pull the front passenger side plug out to see what condition it was in and to see how big of a pain it would be to change the plugs on it as well. After i reinstalled the plug and coil the truck ran ok at first then developed a rough idle and sputters on acceleration. I pulled the coil off and applied spark plug boot lube on the plug wire that goes over the plug and it was fine for a couple of days , now its back . Any suggestions? I also should point out that I also hosed off the engine to clean some grime off of it and was careful to avoid electronics. Dont think this is the problem but wanted to point it out any way. Thanks for reading .

 

When you hosed the engine off, you may have gotten some water in the spark cavity in the valve cover. This could cause one or 2 of the plugs to short to ground and not fire. You may have also damaged the plug lead om the coil when you removed it. If you have an engine fault light on, it should tell you which cylinder if misfiring as well.