...yup, I checked it out ... pretty savvy

 

..:: UPDATE ::..
Swapped Cyl 5 plug with Cyl 6 and fault still present after clearing codes.
Plug from 5 was pretty dirty when removed, when compared to Plug from 6.
Still unable to swap wires to keep on troubleshooting.
SES light blinks when moving forward, but stays solid mostly when stopped at light.
Disco trembles a bit when moving forward, usually between 30 & 60 mph.
Today I noticed new codes while on highway, but do not know when they appeared first, it must be recent, but haven't noticed anything different than when only P0305 was present.
New codes are: P1300, P0305, P0300, P0306 and P0303 ...in that order.
I also notice while on highway that needle for upstream O2 sensor on driver side (02 1x1) dial stays at 0.1 and occasionally goes up, but usually stays there; corresponding dials for remaining 3 sensors do show constant action or seem to be moving in similar fashion. But when driving in city or stopped, 02 1x1 needle does move more frequently, and similar to remaining O2s.
I know that I must swap wires to keep troubleshooting, but with this new scenario, plus erratic behaviour of O2 1x1 while on highway, should I focus on anything different? Please advise.
I was able to capture a screen recording of my Torque app showing these dials while driving on highway and in city, I'll prep and upload a link for you all to see, maybe it will help figuring things out.
Thanks again!

 

I would still start with the wires. .1v on the 02s indicates lean afr, which would not typically be what we see with dead miss but much more common to have plug wire issues causing a miss than lean fuel causing a miss.

 

...thanks for the response EXTINCT ...just to confirm, despite of all new logged codes, you still suggest to keep focus on initial P0305 code and swap Cyl 5 & 6 wires, correct?

 

Well actually now the situation has gotten a little worse, 0305-0303 are cylinders 3 and cylinder 5 misfire and they are on the same coil, 0306 is cylinder 6 so it doesn't make any sense to swap the wires for five to six cuz now they're both misfiring. When you have isolated misfired you can swap individual wires and determine if you have a couple wires bad. Same with coils. How old are your coils and wires? Do you already have spares? If not, maybe think about getting a spare set and go from there.

 

​​​​​​
...now that you mention it, they all are actually 2 yrs old (30K miles aprox) ...were replaced between Oct-Nov 2021 while tracing a "crank-but-not-start" (CBNS) issue that prevented Disco from running for nearly 3 months ...all sensors were replaced then (cam, crank & MAF sensors, along with plugs, wires, coils, and fuel pump). Disco finally was able to start after below dash fusebox was replaced.

As per having spares; I only have a "used" set of 8mm Kingsborne that I had bought in June 2021 and had put in myself trying to fix the "CBNS" issue; but these ended up being replaced, despite just days of use, with a new set at the shop where I took the Disco to deal with the "CBNS" issue -I guess they troubleshooted the issue and preferred to replace all possible culprits down the line of usual suspects.

So most likely I'm better off just replacing plugs and wires at this stage.

 

Ok, well since you have spares you can proceed with the process of elimination swapping known good for question good. Having the coil relocation kit will make it a lot easier but you can do it without it. https://extinctmotorsports.com/land-...elocation-kit/

Since they are new I am a little surprised you are running in to this but it basically is going to be either plugs, wires, coils, injectors, or wiring to the injectors. Or some combination of those. Because you had a shop work on it I am guessing they did something not quite right...

 

Like I said before, shop worked on it back in Oct-Nov 2021 -2yrs ago aprox; but yes, it seems a "fairly" short time for plugs and wires to fail, and Disco had been running "relatively fine" since, and up to less than a month or so ago, when it started running a bit rough and making "weird" noises. I'm also taking into consideration the fact that I neglected to do the regular service on it, and went nearly 10K miles without it -when I regularly did it every 3.5K, then extended it to every 5K the previous couple of times. Please note that recent "weird" noises went away after last service was done a couple weeks ago, including those from cat -which has given me quite a relief for now; but the rough idling and codes have persisted and have our attention for now.

Yesterday I did a similar long drive as the day before -when all those new codes came up as "logged", so I cleared all codes before my drive to see if they came up again. Immediately P0305 came back as "logged" and "pending" at the same time, and P0300 only as pending (P1590 has ALWAYS been present as "logged", but we all know what's that about). After a while driving all "pending" disappeared, and P0305 still showed as "logged", even today; but none of the sudden previous codes came up as pending or logged when I checked. So I will pick up from where we left off and finally replace that cyl 5 wire for now, and report back soon. Thanks again! ;-]#

 

BTW, in this link you'll see a screen recording of Torque app showing the behavior of all sensors during a 40 mins drive (clip was sped-up so it is nearly 10 mins); when the "BLUE X" appears, I got off the highway and continued driving in the city; you'll see 1x1 sensor more active then; also during this clip is when all others codes suddenly appeared. I cleared them all the following day, and only P0305 is the one present from the get-go up to now. I hope this helps somehow, or to at least teach me to understand them all ...thanks! ;-]#

 

That was pretty interesting watching. Looks like you have a vacuum leak on bank one (always runs lean except occasional jumps to rich) and maybe a leaky injector or misfire on bank 2 (0306). This of course is in addition to your misfire issues with the wires. Has the lower intake been off?