Hi all, apologies if this topic has been discussed, I've been searching this forum as well as others for weeks trying to intermittently figure out what's up with my Rover so it seems like it has been but I still don't have an answer!

I'll try to make this as short as possible:

1)Engine started running slightly rough, not too bad but something was up-felt like a misfire to me.
2) CEL came on and I plugged in my OBD II scanner and it came up with misfire codes P0300 P0306 P0303 P1316 as well as a O2 sensor code -bank 1 sensor 1
3) thought I needed to replace 02 sensor but friend with a Disco 2 told me it was more likely that whatever was causing the misfire (plugs, wires, coils) was causing the 02 sensor code and to diagnose those first.
4) I started with the coil packs. I swapped the coils at the firewall -I swapped cylinder 3 with cylinder 2 and cylinder 6 with cylinder 5 and started it up to see if it threw codes for cylinders 5 and 2 now instead.
5) Instead of throwing ANY codes it started backfiring and sputtering.
6) I swapped them back to the correct cylinders and now it has "pending codes" but the CEL is no longer on-but it's also running about the same as it was when I swapped them to the incorrect cylinders. no backfiring but it's basically in "limp" mode it feels like-severe loss of power, I can barely drive it up a steep hill and I can't get it above 20mph.

So I have somewhat of an understanding of mechanics/engines but very little experience actually working on them. Did I swap the coils out at the wrong place? Was I supposed to swap them at the spark plugs instead of the firewall (is that the coil pack?) Or is it possible that the ECU needs time to "readjust" after I put the coils back in the right spot? I have only driven it less than a mile since doing so.

I bought this car partly because I want to learn how to do things myself but I may already be ready to give up on that, haha! I would really like to fix this myself but I may end up just bringing to a mechanic, but I need it running properly before I even do that because there's no way it will make it there without a tow truck at this point. I appreciate any and all help/suggestions!

 

"4) I started with the coil packs. I swapped the coils at the firewall -I swapped cylinder 3 with cylinder 2 and cylinder 6 with cylinder 5 and started it up to see if it threw codes for cylinders 5 and 2 now instead."

Does this mean you unplugged the wires at the coil pack end of the spark plug wire and swapped them? Did you also swap them at the spark plug end?

The engine is built to fire the spark plugs in a specific order which coincides with the position of each cylinder in its combustion cycle. If you just swap plug wires the coil pack will be sending power to the spark plugs at the wrong time.

First thing to do is make sure you have replaced them correctly. You must follow this diagram exactly as shown
.




Then order new plug wires.

I have been using Kingsborne for the last 12 years and my truck has been happy with them. I use the 8mm version.


Spark Plug Wires for Defender, Discovery and Range Rover



Then change your spark plugs. When you do, make sure you have gapped them to .37 ...




Once that is all done let us know how it goes.