Hi all, my MOT is quickly approaching and I (thankfully) didn't trust my 4.2 and took it in for a quick emissions test due to a frequently appearing EML. The code points to both banks post-cat sensors having low voltage, which I understand to be a rich condition. Coupled with the stench of fuel and a pretty chuggy cold start, I'm inclined to agree!

Now, after the first 30 seconds of idling, the engine is as smooth as silk. Feels like all 400 horses are there when warm and doesn't give any hint that anything is wrong. Even fuel economy is "okay" at mid teens.

So far, I have replaced the o-rings on the PCV neck, cleaned the MAF with dedicated liquimoly MAF cleaner, replaced the post-cat O2 sensors and of course given the car an oil/filter and air filter service.

I have two new (unfortunately, Britpart... I know) pre-cat O2 sensors on the way as well as 8 new spark plugs.

Short term fuel trims are at 13.28% on bank 1 and 10.16% on bank 2 after a cold start, and the long term fuel trims are currently at -7.03% on bank 1 and -2.34% on bank 2. Though I have seen the bank 1 fuel trim as high (low?) as -13%.

I cannot see any oil leaks from the valve cover on bank 1 (which i understand to be the drivers side, RHD car) but I can see evidence of oil residue on the PCV valve. As mentioned above, I have replaced the two o-rings but this has not cured the issue.

Would anyone happen to have any pointers I could look into while waiting for the plugs and sensors to arrive?

PS: I have taken Bank 1's upstream sensor out and cleaned it with the MAF cleaning spray. But of course, this has not solved anything.

downstream sensors are reporting as 0.03v (bank 1) and 0.04v (bank 2) when cold idling.

Cheers in advance,
Tom

Replace the maf with a genuin part the chinease supplied one from AF caused me all sorts of issues. I know you cleaned it but replace it.

Cheers Dave. I'm not totally convinced the issue is MAF just yet. The genuine MAF I already have was pretty clean anyway, but I thought I'd give it a clean seeing as I was replacing the filter anyway.

According to live data, the MAF appears to be reading just fine and correctly at 8g/s at idle?

I plug my id tool in tomorrow and check my maf readings for you as a comparison

I realise the 4.2 is a different beast to the 5.0 but have you checked your oil recently? See if it smells of fuel, that was the problem on mine. The PCV was sucking the fuel vapour back into the intake and hey presto rich running.

i would defo replace the pcv with a gen new one oil ingress makes the rubber very soft and distorts it tears easily new vehicle purchase
2007 supercharged 4.2 java black .sand leather vogue se trim
previous cars .
range rover classic 200 tdi
discovery 1 200 tdi
freelander 2 2008 hse
discovery 1 300 tdi
p38 4.0 ltr man r380 ex royal support vehicle on v5c
discovery td5 man off roader

Rackers - Cheers for the pointer. I've recently changed my oil and it did not smell unusually fuelly. It did have a slight stink to it, but nothing different to what I usually smell on my other cars/bikes

Oggy - Thank you! When I took the PCV off, I was able to suck and blow through it as if there was no restriction at all. Almost like there's no diaphragm in it. I've read up on it and apparently, this is normal... But it doesn't 'feel' right!

My running rich issues was the common O ring at the back of the engine yes it's on my sport but dame engine same issues. Also check the vac pipes at the rear. You can see my video here on 2nd page
https://www.rrsport.co.uk/forum/topic59578-15.html

Very useful thank you! Was that leak from the black hose you can clearly see, or was it underneath the supercharger?

The pipe goes into a push fit connector in the top of the block the O ring fails, common issue.

Just to follow up on this issue. It turns out my Precat / Upstream O2 sensors were both dead

Replaced them with Britpart ones (I know, not the recommended brand, but finances were horrific this month!) and also replaced all 8 spark plugs. She went in for her MOT today and passed with flying colours. Fuelling was spot on at 1.006 lambda and 0% HC / 0% CO2.

Thanks all for your input!