Dead cylinder or need new coil pack?

[97sprt4x4]

I can almost confidently say i have the factory coil pack and wires with almost 120k on my truck, (changed plugs at 110). What are some signs that the coil pack and wires need replacing... I've noticed that over the last year my gas mileage has dropped from 15 running about to 13 running about, however i've added a desert bar and upped the tire size from 30s to 31s. as well as the other night i was messing around with my truck in my friends driveway, and i pulled one of the wires out of the pack to see what my truck would sound like with a miss, and the idle didn't change much if at all... so i put that one back and pulled another one, and it did the same thing... then i pulled a third one and it finally started running really rough... do i have a dead cylinder or a messed up coil pack.

 

[97xlt4.0]

That's really weird, I thought anytime a spark plug wire was pulled, an immediate difference would be audible. Hmm.

I would definitely vote for replacing the wires and/or coil pack if you have any doubt about 'em, though!! My mpg dropped recently as well, and I eventually wound up with a CEL and a misfire code. I traced it down to, and replaced, the original wires on mine, with 184k on 'em. Checked my last couple of tanks, and my mpg is back around normal!

 

[robertoa1a]

Coil packs usually don't go bad that easy. Double, triple check the connection!

 

[97sprt4x4]

Is 120k on wires and coil pack a lot? should i have replaced them by now?

 

[storlied]

Check your plugs again, I was debating the same issues.. changed my plugs and it runs like new [pretty much] there's still a very very light "miss" or something but I'm leaning at wires now because the wire going to the worst plug [there was no gap left.. o.o lots of deposits of crap] the wire was very very soft, like it was breaking down sorta.. plugs, then wires.. I'm at 131k or so and I'd probably change the coil packs last..

I also did the pull a wire from the pack thing, tried all of em and nothing changed.. it was odd as I had everyone telling me it was going to tell me the problem. So double check those plugs.