My Supercharged has now done just shy of 2000 miles since all of the work was done and the engine was rebuilt. It’s still running beautifully. When sitting in the car with it idling, you can’t hear or feel it running.

When driving the car it is beautifully smooth and very responsive.

Much to my surprise on Thursday afternoon last week the engine management light came on. When scanning with my IID tool I got a P0172 - System too rich (bank 1).

Click image to enlarge

Click image to enlarge

I've had similar in the past on my BMW where I've found an air leak in the inlet tract pipework/vacuum system causing odd running, and also leaky injectors can cause similar codes
.

An intake air leak can cause this DTC - more likely to be O2 sensor though, not the actual value, just the rate of change can be slow. Diagnostically, I've cleaned them with carburettor cleaner and reduced pressure compressed air (~50psi), this has worked but we'd always change the sensor, mainly because JLR wouldn't pay for cleaning as a diagnostic but would pay the replacement time.

Was that causing rich running?

I’d have thought unmetered air getting in would cause it to run lean.

I did wonder about the injectors too. Kinda hoping it’s not them though as they were all rebuilt less than 2000 miles ago and they’re a sod to get out!

David. 2002 4.6 Vogue SE - Alveston Red with Lightstone Leather
2007 Range Rover Supercharged in Java Black with Ivory 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

It'll run lean until it 'realises' it's running lean, then (over)compensates - which sets the DTC.

Cheers Phoenix.

To prove the point I wonder if I could swap them from side to side and see if the code changes to bank 2 as that would be a quick way to be sure it’s definitely an oxygen sensor.

David. 2002 4.6 Vogue SE - Alveston Red with Lightstone Leather
2007 Range Rover Supercharged in Java Black with Ivory 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

I can't see a problem with doing that!
If it was an injector, I'd expect at least a spark plug to have heavier deposits than the others, if not a misfire or 'pinking' on cold start.

Good point about the plugs, I might take them out just for a look. It really is silky smooth at all times though so I doubt it’s an injector.

I’ll try and swap the oxygen sensors around and see if that moves the fault. Although I guess on an 07 plate at 138k it’s probably worth changing them anyway. 2002 4.6 Vogue SE - Alveston Red with Lightstone Leather
2007 Range Rover Supercharged in Java Black with Ivory 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

It'd be worth swapping them over to prove it's nothing else and save unnecessary expense. If the fault does move with the sensor, given the age (and presuming they're originals) it'd be good preventative maintenance to replace both. There's no teach-in process, they're just fit & forget.

David

If your O2 sensors are the originals then I would change them, from my research when I had a similar problems I found a few references that said they have a life of 100,000

I had one changed but still kept getting spurious errors, since changing them all these errors have gone.

David

Edit My original fault P0171 (lean) was caused by failing Post Cat sensor, these are very cheap (£45) so maybe try that first. Range Rover 4.2 Supercharged 2006
Ford Focus EcoBoost 1.5 2017
MG TF 2003

Previous Cars of note
Land Rover Discovery 2
Jaguar Mk2 3.8 - Company car
MG Midget 1974 - Concours

https://www.fullfatrr.com/forum/topic55398.html

worth a read

i never fixed my issue and just sold the car.

but one thing that was important was hooking up SDD and looking at the adaptive fuel trims since it shows both banks

if its just 1 bank then you can narrow it down a bit, common components like MAFs wont matter.

also a smoke test never hurts.

also these cars are really funny if the sensors are OEM. Especially with MAF. Its actually a sport

Not anymore, 4.4 TDV8 now

Few more observations today:

On Thursday I reset the adaptions so that I could keep an eye on fresh data. I’ve now done about 50 miles since. After 20 miles up the M8 with the car idling these were my long term fuel trims:

Click image to enlarge

Click image to enlarge

Think am going blind 😂 thought you were saying too lean.

I think you can see the injector timings in gap, might be some clues there Its actually a sport

Not anymore, 4.4 TDV8 now

All 8 of them are virtually identical.

The injectors were rebuilt before being refitted so should be ok. Well, fingers crossed anyway! 2002 4.6 Vogue SE - Alveston Red with Lightstone Leather
2007 Range Rover Supercharged in Java Black with Ivory 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

dhallworth wrote:

After seeing how close they are now with the engine running I’m inclined to lean more towards something common to both banks.