2002 SE Possible Misfiring?

My girlfriend has a 2002 Ford Focus SE. A while back she had acceleration problems, hesitation when giving it the go - we replaced the coil pack finding that 1 of the connectors was dull and the the other three shiny. We also replaced the plugs with Platinum 3 that are gapless and replaced all new plug wires then the car ran perfectly! That was a few months ago. Just today the car started shaking and emmiting kind of a foul smell from her tail pipe. The sound is like a holllow puh puh puh puh puh. The CEL light is on and when idling the engine seems like it's being over worked by shaking almost like it is running on 3 cylinders. If the coil is bad again could it have different symptoms than before? What are the odds of the plugs going bad again or the wires since they are brand new or could it be the Catalytic converter? We don't have much money and want to avoid a repar mechanic if possible. Is it driveable without damaging it further and any suggestions??????:banghead: :banghead:

Chances are fairly slim that the plugs or wires wouild be bad again in such short of time. It does sound like it is running on 3 cylinders. Could be a spark plug boot is loose on the insulator causing a misfire for that cylinder. You can tell which cylinder by pulling wires one by one and when the sound of the motor doesn't change after pulling the wire you will know that is the bad cylinder. When you find the bad cylinder, pull the spark plug and check the gap. Has it been mashed down. Couild be from a dropped valve seat for that cylinder. When you have the plug out ground it while the engine is running to see if it is firing. If it is you have a compression problem which will indicate major engine damage. Not the cat if you don't get a CEL code on it. Take it to Auto Zone if one is in your neck of the woods and get the codes pulled. Once you have, post them and we will determine what is at fault. They won't charge you at AZ to get the codes pulled. They will charge you at Ford.

If CEL on then definetely have the codes pulled and post them up. As far as plugs go I've never really heard of gapless plugs like u said u had replaced them with but my advice on that is to replace them with factory ones. Ford engines are very picky about their plugs and although expensive its a good investment.
If i were working on this car heres how I would go about it. Spray water on wires/coil to see if anything arcs over. Remove all plugs keeping track of which belongs to what cyl. check them for proper gap(don't know about yours) check the color of the porcelin should be a light tan seeing as how it hasn't been that long since you replaced them, look for cracks in the porcelin. If you dropped them assume they're bad. Post back if all ok or any defects found.
As far as driving it I wouldn't do it too much sounds like you have an ignition problem which means all that raw fuel is going through you Cat. Converter and will eventually fry it. If your able to narrow it down to one cyl and you must absolutely drive the car disconnect the injector to it and then you can go ahead and drive it. Oh and if you do find out which cyl is at fault swap out the plug with one from a different cyl see if it the miss follows the plug.

Forgot to mention this if you drive it without disconnecting injector and CEL starts flashing pull over as soon as possible and turn car off. This means a gross emissions fault has been detected and in your case you re causing damage to the cat.

I guess I didn't mean gapless - It means the Bosch Platinum 2's I put in don't require physical gapping. I pulled the plugs and the first one I pulled out, all of the ceramic is black. The other three are light tanish brown. So I can see that is the one with the problem so I went out and replaced all 4 plugs with OEM recommended and the car is still having the same problem. Is there a special way that I can tell if the coil is bad again? It is a cheap one from e-bay....maybe it just didn't last. The wires look good too - no issues there. I am thinking the Cat is shot or the coil is bad. I hope it's not a compression problem. :disappoin

Since you've narrowed it down to one try doing a compression test and decarb your engine. If by any chance you have CEL on try getting codes pulled it your problem could be caused by a bad injector, coil like you said, MAF sensor, TPS, a number of things but the codes will help narrow it down considerably.