Misfire and Stumble under load '01 Focus

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Yes, that's my understanding of what can happen in a wasted spark system. One or the other plug can fire but then there is a lower resistance path (short) in the coil somewhere that makes it easier for the circuit to be completed through the short in the coil than continuing and firing the next plug. I'm not at all an expert but this is the way I understood it.
 
Further evidence today; I removed the coil and two of the mounting ears fell off. There are also some cracks through the body of the coil pack.
 
Had this issue once, I hastily concluded that it was a clogged fuel injector (it wasnt) unable to meet the demands of 50%+ throttle. Changed injectors, same problem.

What it turned out to be was a spark leak. At idle and light throttle, the combustion chamber pressure is low- mostly all in vacuum- so there is less resistance across the spark plug gap. Once you open the throttle and the cylinder pressure/charge density increases, the resistance across the plug gap increases and the voltage leaks to a less resistive path.

In my case it was the plastic boot that extends into the head down the spark plug well. It was cracked and grounding out to the spark plug tube. I suspect that your problem is the same- either than internal leak within the coil or somewhere along the wire to the plug.
 
Plugs and wires are new as of 12-2015 so I think I'm all good there.

If not the wires have a 'Limited Lifetime Warranty' from Advance auto. On that subject, has anyone ever tried to claim on one of those warranties? I did notice that my #4 plug wire needs to be pushed down hard on the plug to get it to snap on. It's almost like the terminal inside the boot is up in too far. Another issue I may have with trying to return those is that the receipt (paid online, picked up in-store) says Carquest brand wires but what I got was Autolite brand. I was okay with it at the time as I felt they went well with my Autolite double platinum's and seemed to have better reviews than the Carquest brand.
 
Well I think it's all fixed now. I installed the new coil and soldered on a new connector. It runs fine at idle and revs ok, the true test will be out on the highway but I'm pretty confident it will be good. Here's what the old connector looked like, it's no wonder I had a misfire.



Here is the repaired connector, soldered and heat shrink tubed.



I put the factory wire loom junk back over the new end of the wire but I feel like I need to cover the rest of it with something.




I also noticed, as I was soldering it that there were a few broken strands in the factory side of one of the wires. I hope it's just a result of the harness being too short and not an indication of what the rest of the wiring in the car looks like.

So what say you BITOGers, plastic corrugated loom stuff will be sufficient for covering and protecting my splices?

Also, the new plug, because it was technically not for this application, did not have a rubber seal. The old one was pretty stretched out but I reused it anyway. Between that and the dielectric grease that came on the new connector I think it will be ok.
 
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My 2002 Focus Ztec had the same problem but the wire was broken inside the shielding and I did not see it. When I stepped on the gas the movement of the engine was enough to break the connection but not all the time at first. I also had 2 broken ears on my coil and had replaced it with no change. I read on a Focus Forum about the harness problems and wiggled the wires while it was running and found it right away. I went to the local salvage yard and they gave me a harness for free. I soldered my wires, covered them in heat shrink tube and the plastic loom sleeve also. I covered it all with electrical tape. I tried to keep the wires from having a lot of movement hoping it will last longer. I did mine 2 years ago and it still works, but I expect I will have to replace it again some day due to using a used harness.

I also had to do the same repair to the alternator pigtail on my Kids Ztec Focus. Watch for that in the future as well as a thermostat housing leak. Aside from a few common things both cars have been very reliable.
 
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Originally Posted By: Ifixyawata
Starting Tuesday, I noticed that starting out in 1st gear, anything more than about 25% throttle will result in bucking.


My Buick had that same problem last year. It needed a new MAF sensor bad. The computer would set a MAF code and then erase it on its own. Tapping on the MAF sensor while watching the scope confirmed a bad MAF sensor. They're not supposed to spike when you tap on them.
 
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