OK just swapped COP8 with COP5 and cleared the codes. I am hoping that since#8 is the only one that threw a legit P0308 code that it was setting off the P0351. I'll be driving home in a few hours. I guess we will see how that goes.
I had this same problem many and many of times, it sucks I know, but every-time for me on cop8 that has oil in there as well it throws off a odd code for some reason.
ok example: car would tell me 4 was bad when it was really 8, but I saw 8 a while back before I started changing coils so I replaced 8 and 4 hasn't miss fired since.
ok my thoughts on why from my experience,
Coils 5-8 have oil, and I haven't fixed it and I now leave the covers off for 2 years as a test and have not gone through as many coils. My take is moister, oil is getting hot and then cold, under covers it creates condensation, well if you leave covers off the oil can evap and it wont drain and smell running down the engine.
That has been working for me though as I don't plan on having this car much longer "2002 ls v8" 84,000 miles
Another test you can do that has worked for me to make sure it isnt tricking me, is while the car is on take off the wire going to that cob and see if idle get worse or not.
you said internet on the cobs? good luck! huge mistake I made, cheap is NOT good, go to napa they have a cheaper one and a more expensive one that is new, get that one it is coated better.
Now you will also notice that you can drive the car for at least 1/2 hour then start hitting hills and the car starts misfiring then you wake up and car is running good all of a sudden, well that tells you huge amounts of oil is going from cylinder 5-8 as it gets warm it moves easier. then the boot is now so swollen it is arcing on the side casing misfire to other coils also.
Also, get oil cover fixed, the reason this happens is because, the engine had more power than the cover design. but there is a fix for it I believe.
There are also wires under the Big black round cover green wire likes to rub on a bolt, make sure that is not grounding out. its the upper right cover i believe for the shocks or struts or whatever.
Check fuses EVERYWHERE especially in the trunk there is a few computer fuses back there and they blow easy and on both panels in the front driver and front side passenger, look carefully you may have to pull every fuse out.
Sorry if messy I just in a hurry good luck.
Hope some of this helps, also note: weather changes from winter to summer and summer to winter is when most happens, I replaced this spring 4 in one week, don't bother the swapping them around just replace them as they go, you will get so good at it you can drive around with a spare one and replace it in under 4 min. my record i think is about 3 min. Only because I don't bother potting the covers back on, I figure whats the point.
One Last advice, The v8 ls they do not like to IDLE, don't warm the car up for long times in the morning or let it sit running. That is when you blow coils allot.
