2016 SCV6 Bank 2 misfire

[ebp02]

Hey guys, I'm new to the forum. Bought a 2016 LR4 scv6 with a blown engine for a good price, swapped in a low mile XJ engine about 4k miles ago. Everything went pretty smoothly, changed seals and upgraded coolant pipes and yeah all the bits. Love the LR4. anyways about a week ago I was finishing the truck by finally putting on the splash shields/ engine guards and the cosmetic engine cover and the truck started misfiring on me. I had driven the thing for about 3k miles without any issues. so, I figured maybe a ground or something. codes were P0356, P0300, P0304, P0305, P0306, P0354, P0355, P1315. Turned off the truck and fiddled with the engine cover and they went away after clearing the code. Today I was driving on to a highway and went over a couple of potholes and the misfires came back, except this time it only was P0300, P0304, and P0305. I was in a parking lot with a hot engine and limited tools so I did the ol engine cover trick and yeah no go. Then I took the engine guards off and peeked and saw noting. Got the truck on its way home via tow truck so still haven't gotten to mess with it but I can throw the coil packs from the other engine on it, read crank sensor somewhere, don't understand how it could only affect one bank without it being out of time and no camshaft correlation codes and only 2 cylinders this time. I'm thinking injector ground but again only 2 cylinders this time. maybe bad luck. Read O2 sensor too but again 2 cylinders only idk. Reset the CEL a few times and only the 2 cylinders kept on coming back. I guess I'm looking for someone who can point me in the right direction from experience.

TLDR; messed in engine bay resulting on bank 2 misfires Cyl 4,5,6 fixed by messing with engine bay and resetting the CEL. 1k later bump sets off Cyl 4,5 no go with just tugging at the harnes lol. Truck will be in the driveway in about an hour and would love to have an idea what to fix.

Did use denso spark plugs on all cylinders so idk I trust the brand but I know NGK is oem. Also only those cylinders are misfiring.

 

[ebp02]

Also got spare injectors but I'd like to avoid cause of seals but obviously would change if that the fix.

 

[jlglr4]

When you had the first round of codes, you had some coil codes there. Do you know if these were old or recent? If you printed them out, might have dates associated. If those codes are recent, that’s where I would focus my attention first - and specifically the wiring harness and ground since you have codes on multiple cylinders.

That concern aside, and at the risk of sounding like a broken record on this forum, I’d check fuel trims next (seems like you have a scan tool). Might point you in a direction. Check with car in park or neutral, at idle, then 1500 rpm, then 2500 rpm (hold throttle steady). Add short term and long term together. Zero is perfect, anything +/-10% is considered normal range. These cars separate fuel control on each bank, so I’d be looking at things that would affect one bank rather than both, e.g., o2 sensor, injectors, etc.

 

[scapistron]

Bit of a long shot, but low effort to swap plugs and coils between 1 and 4. Little bit more effort and you can include 2 and 5. Also give you a chance to look at the plugs.

 

[ebp02]

Changed coil packs on 4 and 5 from donor engine and no change, checked sparkplug on 4 and looked ok so while running I started tugging at the harness and noticed a change in idle so I followed the ground and noticed it was loose enough for the ground to wiggle around. Probably why it misfired that first time while putting the engine cover on and for the bump to wiggle it. Tightened it and misfire is till there. I wonder if there all that messed up injectors 4 and 5 so I got new seals in the way and I guess I'll replace the injectors with donor ones. Did look at fuel trims and they look good to me but idk y'all let me know how they look.

 

[ebp02]

Here's come of the screenshots

 

[jlglr4]

I’m not sure what I’m looking at in those graphs. If that‘s showing 30% to 40% (or -30% to -40%) on the fuel trims, that is not good by a long shot. You should be throwing codes at that level. Am I reading it wrong?

 

[ebp02]

Update.

Worked on the Rover on my time off, luckily it's a 3rd car. Around Thanksgiving I had it narrowed down to no spark, checked the wiring and the coils and it all checked out good so figured the ECU so I sent it out to get fixed. It came back right after Thanksgiving and it was all the same so with holidays and whatnot I didn't get to work on it much. Went back to testing and yeah ECU still seemed to be the problem so this time I decided to source an used ECU. Put the clones ECU and it all the cylinders came back to life. Drove a few hundred miles and P0430 came up, catalyst efficiency below threshold bank 2 so yeah I hope that'll clear in a few miles. Didn't drive the car but more than a mile but did let it idle probably a total of 30 minutes a few minutes at a time over the months it was down.

Here's a random Chinese video of the issue/what I hoped the first shop would do to my ECU.

TL;DR
Loose ground caused a chip in the ECU to fry, cloned ECU and things back to normal minus CAT which hopefully needs a few miles to clear out some unburnt gas.