My mom has a 2000 Mountaineer with the 5.0L V8. Lately we've noticed that it makes a Ticking sound when it's running. Also, the motor tends to "miss" when youre trying to hold 40mph. The plugs/wires have recently been changed. It started doing this ticking and missing a few weeks after I did the plug/wires, I hope that's not part of the problem. Ive read many threads on here about the 4.6's and 5.4's ticking being caused by anything from an injector to an exhaust leak, but nothing for the 5.0. If anyone has any Ideas just shoot them this way, thanks

 

That's a distributorless engine, right? I'd start by checking for spark leak - do it at night with the underhood bulb pulled so it's dark. Any spark will be easy to spot.

If you can't see anything, use a mechanic's stethoscope (or just put your ear to a long screwdriver pressed against the engine) to listen inside the valve covers, oil pan, fuel rail, & anything else suspicious.