97 5.4 running rough
Hey, guys. I'm new here, and could use a little help. Just picked up a 97 5.4 Lariat 4X4. The truck is fine except for a skipping issue. When I first bought it, I took it to my mechanic and he did a full tune up. Plugs, coil packs, PCV valve. The works. It was fine for about a week or so. Then, it started cutting back in the upper gears, especially OD. The truck jerks and rattles, cuts back, and lopes out of the tail pipes, almost like it's misfiring. But when you hit the throttle and it downshifts, it evens out like there's no issue. I'm stuck on this one. Any help would be appreciated.