I have a 1998 F150 w/ 4.2L. The truck and engine have 253,000 miles on it and it's been running wonderful. Now this could be just a coincidence, but I ran a small bottle of Lucas Injector/Fuel cleaner through the last tank of gas. All of a sudden I have loud tapping noise at start up that lasts for a couple of miles at least, then it just stops making the noise and sounds perfect. If, during the same day, I let it set for a period of time, it will have another tapping sound then after a few minutes/miles it completely goes away again. I've taken very good care of the engine changing the oil regularly, I use Castrol 10w40 in summer and 10w30 in winter ( I live in Oklahoma, so no harsh weather really). But the noise really concerns me. The thing is, when the sound stops after a mile or two, the engine runs and sounds perfect. Any ideas?:santa:

 

You should not be using 10w anything - the specs are for 5w20 or 5w30. What are you using for an oil filter?