Learning this cars systems has been through reading an re-reading thru the huge factory service manual that I bought for this car, as well as the knowledge I learned through the many years as an Airline mechanic.....
I had a P0301 misfire fault, an it turned out to be a failed fuel injector If what I posted is confusing, I'll try again after (yep) another reading of the service manual.
It doesn't sound like a faulty crankshaft sensor. But being electrical, weird stuff happens.
This is what I love about your posts. You don't just spew out a bunch of technical jargon and specs without actually explaining it. You take the time to educate and enlighten. As a novice DIY, I really appreciate that.
I've been a sort of "mechanic" in the aircraft field myself for nearly 20 years. Not with engines but from the avionics and cabin equipment side. As for cars, I've been doing basic maintenance like oil, brakes and belts etc for even longer. Only in the last 10 years or so have I been getting more adventurous. Mainly for the sake of saving money and due to a few experiences with some very shady shop mechanics. Now, everything is a learning experience. I don't know much but I know enough to recognize when a job is beyond my capacity.
As for this issue, I think I understand your explanation pretty well. Same friend that found that article also found information that suggested a faulty crankshaft sensor could cause this problem. If by "circuit" you mean the electrical pathway to the plug, then no, cylinder 5 is not ok. Using the in-line spark plug tool, I can see that there is a definite intermittent disruption of electrical power getting to the plug.
What I've done so far is replace all of the plugs and wires with new. I've swapped coils on both 5 and 6 with other cylinders. No change. Even though it only popped up once, I've replaced the B2/S2 oxygen sensor because I got code P0157 when this whole thing started. I used a mechanic's stethoscope to listen to the fuel injectors and they all sounded the same to me.
I have not checked compression or electrical power going on cylinder 6 yet. I can and will try to do that next. I only say "try" because as we all know, the passenger side of the engine is a real pain in the ass and I can't promise that I'll be able to get the compression tool in there. I will also do the resistance check on the fuel injectors on 5 and 6.
For cylinder 5, I'm eventually going to have to start looking for the cause of that intermittent disruption. Can you recommend the best method for doing that? Obviously I'll start by examining the harness connector and wires for the coil. Is it safe to put a multimeter on those contacts and if so, what kind of readings should I be getting?
Thanks again for your help.