What would a stuck lifter do?

[96fourbanger]

What would I notice if I thought my engine had a stuck lifter? The thing has always made noise and gotten horrible milage (12-13 mpg). Noise is worse when it's really cold outside or driving up hill/into wind/under any kind of load. It's loud enough to sound like a diesel. I bought it used a few years ago and noticed a slight noise then but it's getting progressively worse. Sound is like some kind of valve train clatter. I'm at a loss. I just know it shouldn't be this loud. No codes thrown, spark plugs and wires changed in the recent past (motorcraft), regular oil changes. Any takers? I just know there has to be something that I can look for. Lifter makes sense but I don't know enough about engine internals to know if that's really a good place to start looking. Plus, would rather not open up the engine if I don't have to. Any takers?

[BrianA]

sounds like it could be a lifter or rocker arm.

You might want to try using a mechanic's stethascope to pinpoint the noise source. They can do a very good job sometimes zeroing right in on the source of the noise.
At least you'd know if you did or did not need to open up to inspect the valve train.

Best of luck and keep us posted on what you find.

[dennisinmo]

Just throwing out something here. Check spark plug wires are going to the right plugs. Two crossed wires could give you a bad ride. They could have been crossed when you bought it and you copied the miss wiring.
Good luck