so bit of an update issues still not gone away but getting closer.

so on running just lpg for about 200ish miles. i only get lean codes for bank 1. so time to gives both cylinders the full treatment ie coils and plugs.

but when running petrol both cylinders have issues. so now I'll be dropping the tank soon i'll try and change fuel filter.

Last edited by mgrover on 8th Jun 2020 3:03am. Edited 1 time in total

You say cylinder 1, Im guessing you mean Bank 1 (pedantic, but keeping the peps informed)
Do you get a slight rough idle on a cold start up? feels like a little wobble from the drivers seat (before driving that is)
Looking at this more and retracing this thread Im leaning towards a bung coil or Spark Plug

On my other L322 with the GARBAGE M62 engine I was chasing a slight oil leak yesterday, crawling around under it I notice the post cat 02 sensor is unplugged completely and looks to have been this way a long time (no DTCs every recorded)

Sorry yeah bank 1.I've edited it now.

Yeah slightly rough startup. When I removed a spark plug from cylinder 1 recently it looked lean with an orange tinge so I think it's time for a service. I might just do oil and the lot

With super charged engines a cooler plug is installed so we dont burn holes in our piston crowns.
After you have changed plugs and the coil pack there is only one other thing to really do in that region and thats the injector, looking through your extensive list of replaced items its got to be getting frustrating by now.

You didn't mention but have you replaced the o2 sensors now I guess? did it make any difference? have you done the man with genuine too?

What I don't get is if I runs ok one one bank on gas not on petrol its not likely to be plugs is it? gs is more fussy about spark than petrol. It won't hurt to change them but I don't think it will be that. Same can be said for the coil, the leg is still using the same cold.

I think yous be better off doing the filter for the fuel and maybe an injector clean as it points to a fuel system issue as opposed to spark.... Just my 2 pence worth anyway Current stable:
2006 BMW M6
2007 4.2 V8 S/C FF
Gone:
2002 4.4 V8 FF

nah nothing on the sensors/maf yet.

i wanna fix the bank 1 issue on lpg first, and then maybe bank 2 on petrol is an entirely separate issue. ie plugs are a bit on bank 1 so it throws issues on about petrol/lpg and bank 2 has fuel injector problems.

Hi,

I don't know if this will help but I had similar issues with mine and I then decided to try premium fuel and then gave it an 'Italian tune up' and the issue has not returned. I've not returned to standard unleaded. Range Rover 4.2 SC
2 Range Rover Classics - one from new but both rusty now.
Rover 3.5 Coupe had since new.
Subaru Legacy 3.0.
BMW K1200RS.

Also mGrover what if the o2 sensor is causing that bank permanent problems regardless of the fuel? If you have them just get on an change them it’s a 20 min job if you get it nice and warm and if you already have the maf 5min. You can rule them out the. And yea I agree plugs and coils next shout... but why not swap the plugs and coils from bank to bank and see if the lpg switches bank? If it doesn’t it’s not that and you can move onto something else or maybe the lpg just needs a tuneup after the heads being off! Current stable:
2006 BMW M6
2007 4.2 V8 S/C FF
Gone:
2002 4.4 V8 FF

Haylands wrote:

So if the downstream ones can effect the fuel trims then a worn of faulty catalytic converter will effect the fuel trims..?? Maybe that's a reason for rich or lean codes..?? Or have I not understood that..??

They do like to make things complicated...!!

Danwilderspin wrote:

Also mGrover what if the o2 sensor is causing that bank permanent problems regardless of the fuel? If you have them just get on an change them it’s a 20 min job if you get it nice and warm and if you already have the maf 5min. You can rule them out the. And yea I agree plugs and coils next shout... but why not swap the plugs and coils from bank to bank and see if the lpg switches bank? If it doesn’t it’s not that and you can move onto something else or maybe the lpg just needs a tuneup after the heads being off!

Iirc it needs ngk and why are you swapping into the same bank if you are trying to see if you misfire mows banks? Sure 1-2 and 2-1 would be better and swap the plugs over too? Current stable:
2006 BMW M6
2007 4.2 V8 S/C FF
Gone:
2002 4.4 V8 FF

do you know the exactly part number? i dont wanna drop £80 on plugs that don't fit am guessing NGK Iridium?

no but I'm pretty sure if you put your reg in the cp4l website it comes up with the correct ngk ones the more expensive ones. Current stable:
2006 BMW M6
2007 4.2 V8 S/C FF
Gone:
2002 4.4 V8 FF

are they the iridium ones though? or just "better"

I had the same issue on my 4.2, went through all the same things you did, have you by any chance done a compression test?