thensley

My 1998 F150 4.2L V6 on start up has a tapping sound in the engine for about 5 minutes (sometimes, not always, many times it starts great, sounds good with no tapping but still a little rough) and feels, well the only way I can describe it is it feels like it's lugging, struggling to run. Runs better when it's warm, but still idles rough. Haven't changed plugs in a couple of years, but what about the tapping sound? Can't afford to do much, business is lousy. One other thing, I keep losing coolant, but it's not on the ground. Please tell me it's not a head gasket. I'm not a mechanic. Truck and engine have 250,000 miles on it and has always ran great. Changed oil every 3,000 miles, put good gas in it. The tail pipe is a little black but not overly sooty, just a little. Drove it 200 miles today on the highway and it purrs right down the road and mileage is good. Doesn't use much oil at all. Bar's leak has a product for head gaskets, would this help at all and is it safe to use it? The oil looks clean, no evidence of water at all. Totally confused.