I've been battling a lean on bank 1 code for a little while now. So far I've (in no particular order):

Had the inlet in pieces and rebuilt with new gaskets from the head up.
Smoke tested the inlet system - No Leaks
Replaced the PCV valve - twice
Sprayed around to check for vacuum leaks
Replaced the O2 sensor, pre-cat.

I have noticed that the PCV seems to flow a lot of air at idle, and the fuel trims seem to indicate that the fueling is out mainly at idle. If I stop the PCV flow at idle, the fuel trims head back towards zero.

Any thoughts? 05 L322 4.2SC
2016 Discovery 4 Graphite
Lotus Carlton
Ascona 400
Volvo V70R AWD manual
Suzuki 1200 Bandit
Velocette Venom
BMW R80/7
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As it's just one bank it could be injectors...??

Or possibly the other downstream lambda sensor...?

These are just some guesses  Pete
__________________________________________________
2014 L405 Autobiography SDV8 4.4 Loire Blue Ebony interior
2011 L322 Vogue SE 4.4 TDV8 Baltic Blue. Sold
2012 L322 Autobiography 5.0 Supercharged Ipanema Sand Sold
2002 L322 Vogue 4.4 V8 Epson Green (Fatty Offroader) Sold
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Thanks. Injectors is a possible I guess. However, the car also has LPG and the same issue happens on LPG. Hence I figured it must be air related. The PCV flowing at idle seems to be significant?

I discounted the downstream sensor (post Cat), because I figure that just checks the Cat is operating and has no input to fuel control. 05 L322 4.2SC
2016 Discovery 4 Graphite
Lotus Carlton
Ascona 400
Volvo V70R AWD manual
Suzuki 1200 Bandit
Velocette Venom
BMW R80/7
Daimler V8 250
Mini Cooper S Works 2006

Ah, you didn't mention LPG, if it hasn't had a valve saver fitted, and more importantly, topped up and used, then you maybe suffering from valve seat recession...!

Do a compression test....  Pete
__________________________________________________
2014 L405 Autobiography SDV8 4.4 Loire Blue Ebony interior
2011 L322 Vogue SE 4.4 TDV8 Baltic Blue. Sold
2012 L322 Autobiography 5.0 Supercharged Ipanema Sand Sold
2002 L322 Vogue 4.4 V8 Epson Green (Fatty Offroader) Sold
-Click for Project Fatty off roader-

Valve saver by the gallon. Its only done about 15k miles on LPG. Compression test done and no issues. 05 L322 4.2SC
2016 Discovery 4 Graphite
Lotus Carlton
Ascona 400
Volvo V70R AWD manual
Suzuki 1200 Bandit
Velocette Venom
BMW R80/7
Daimler V8 250
Mini Cooper S Works 2006

Remove your MAF, give it a good soaking with electrical contact cleaner, let it dry and then refit it.

Mine started to occasionally throw a fault and ran a bit lumpy, cleaning the MAF feels like it made a big difference.

For the sake of a £4 tin of contact cleaner it's worth a try

David. 2002 4.6 Vogue SE - Alveston Red with Lightstone Leather
2012 Range Rover 5.0 SC Autobiography in Indus Silver with Jet/Ivory Interior
2012 Range Rover 4.4 TDV8 Autobiography in Baltic Blue with Sand Interior

Apologies, should have said, I've cleaned the MAF, twice I also assumed it would impact both banks equally, but bank 2 is quite stable on fuel trims. 05 L322 4.2SC
2016 Discovery 4 Graphite
Lotus Carlton
Ascona 400
Volvo V70R AWD manual
Suzuki 1200 Bandit
Velocette Venom
BMW R80/7
Daimler V8 250
Mini Cooper S Works 2006

I'm reaching the bottom of the barrel now

I'm also selling the Disco 4 this weekend as its currently worth £2000 more than I paid for it 2.5 years ago, so I need the RR sorted so I can tow the caravan. Nothing like a deadline to focus the mind  05 L322 4.2SC
2016 Discovery 4 Graphite
Lotus Carlton
Ascona 400
Volvo V70R AWD manual
Suzuki 1200 Bandit
Velocette Venom
BMW R80/7
Daimler V8 250
Mini Cooper S Works 2006

My money would be on pulling in air on bank 1 somewhere.

I agree. I cant find anything other than high flow through the PCV valve back into the throttle body. If I block that flow, the fuel trims settle back to around zero.

Should the PCV flow at idle? I'm unsure how it is supposed to work. 05 L322 4.2SC
2016 Discovery 4 Graphite
Lotus Carlton
Ascona 400
Volvo V70R AWD manual
Suzuki 1200 Bandit
Velocette Venom
BMW R80/7
Daimler V8 250
Mini Cooper S Works 2006

If its a 4.2 sc, thats where I had major issues getting the hoses that plug into the pcv to seat, its a poor design imo, I ended up removing the pcv and taping up the connectors with self amalgamating tape, it stopped a constant problem I had with vacuum leaks on the system.

Eta it sucks like a crack whore looking for her next fix

Thanks. I had the same problem with the hose. Bought a new one (£120+ !!!!) and that was poor too. Ended up with a "temporary" piece of 22m id hose and a couple of jubilee clips. Not pretty, but sealed!

Fitted second new PCV Monday night. Now just awaiting the light to come back on ..........

And useful to know it breathes heavy anyway! 05 L322 4.2SC
2016 Discovery 4 Graphite
Lotus Carlton
Ascona 400
Volvo V70R AWD manual
Suzuki 1200 Bandit
Velocette Venom
BMW R80/7
Daimler V8 250
Mini Cooper S Works 2006

Do you sometimes have the viscous fan running for what appears to be no reason? Usually just a few minutes after you have just started up?
Or a pending p0116 code?

Not at a time which I would say isn't appropriate and the only fault code is the lean on bank1 code (P0171?). In actual fact it is running really well with no issues noticeable. What are you thinking? 05 L322 4.2SC
2016 Discovery 4 Graphite
Lotus Carlton
Ascona 400
Volvo V70R AWD manual
Suzuki 1200 Bandit
Velocette Venom
BMW R80/7
Daimler V8 250
Mini Cooper S Works 2006