I haven't had the plugs out of my '99 yet as Ford replaced my 5.4 last year due to wrist pins. But I was reading a thread on this site you might want to check out under "Engines", " Living with blown out spark plugs". In it they were saying you need a special extra-deep socket when installing the plugs. Otherwise, you may think the plug is tight when it really isn't. I could see where that could easily cause a slight compression leak giving you a rough idle. Hope it helps

 

Thanks, Crash. Now that sounds like an easier way to work!

 

Just thought of another question based on your post Crash.

Since I don't "need" double plats because of COP, do they do any harm? In other words, could they be contributing to the issues I have with my idle?

Are there any issues with slightly moving the injector connectors out of the way by rotating them 15-30 degrees in their holes?

Any truth to the statement above about needing a special socket to tighten the plugs?

 

before you tear into it, i would (speaking from experience) check the 'it's so simple it's stupid'stuff. Are you sure you didn't cross a wire? Did you open the hood at night and look for sparks coming from the wires? (a primitive ohm test) Is the cap cracked, have any scores, burn marks, corrosion, etc? same goes for the rotor. Is it the correct cap/rotor/plug? Don't automatically trust the counter guys at pep boys!
Finally, make sure your wires are isolated and not crossing/touching others. You might just save yourself some work. good luck.

 

Try what Crash said by removing the injector plugs one at a time you should be able to find the offending cylinder. It's veary possible you cracked the insulator on one of the plugs. It happened to me once and the result was the same. I found the crack in mine by rubbing my greasy fingers around it and the grease outlined the crack, Although i had a head start on you as i had a feeling i cracked it by tilting the socket while tightning.

 

Hey Crash!, thanks for the injector connector tip. That's a damn good way of checking which cylinder it is even if it may not be the plug (could be injector), etc.

 

Thanks, Crash! Your injector disconnect tip is great. I love this board. The people on here have tricks that you won't find in any manual. I'm filing this one for future ref.

 

OK, I gave up on trying to band-aid fix it.

Bought a whole set of AWSF32P Motorcraft plugs, gapped them and installed them in place of the ones I'd just done.

Found where I'd put some antisieze where I should have put dielectric grease on 2 plugs (I must have been tired), but other than that I couldn't find anything else wrong.

Time will tell if the idle rough/miss is gone. So far it seems to be.

 

LOL... anti-seize compound... hahaha... tired and one too many beers (but you need them to curtail the cursing as you change the plugs while simultaneously skinning your knuckles!

Anti-seize is actually part petroleum products and part metal powders so I would say it's fairly conductive and was probably shorting those plugs out.

Good to hear it's fixed for now.