am running out of ideas. lean codes in both banks persist always together, its also managed to set off the knock sensor and has some misfires albeit no codes for them.

this is what's been done:

1. pcv replaced
2. maf replaced
3. both top ends rebuilt with hardened valve seats
4. pcm flashed to the latest update
5. air filter changed for a mann cross
6. dumped a lot of redex into fuel tank and cycled

anyone have anymore ideas? i think throttle body is next but that can be a bit of a ballache to get to. or fuel pump being .

this car is hooked up to lpg but thats not working atm so i haven't been using it. the lean codes atm are strictly on petrol.

these engines are a bit of a pain throwing lean and rich codes.

Check for vacum leaks

smoke test was done with no issues

Make sure oil cap is seated correctly to as that can effect the air in the block or it did on mine

seems to be sealed correctly but i noticed when i was trying to twist the cap closed the actual pipe twisted as well...could that be it?

also when am sat at idle, then just floor the out of it at 5-6k revs I hear a thud. could that be a misfire and pointing even more to the fuel pump?

Not sure you can try and see if it helps

bit of an update on this, only thing left is the lambda sensors. i know everyone says they should be functioning fine if their throwing those codes because they've already done a wellness check. but there cheap enough to replace and am almost out of ideas.

My 4.2 sc 05 is on lpg and also has the lean mixture codes. I shall follow this thread with interest as I haven’t sorted mine..

ive done all sorts. supposedly it was VSR due to the lpg, but the heads been rebuilt with hardened valve seats so I doubt its that. i think next ama replace the sensors.

mines lean no matter if its lpg or not

Everyone said that to me too but was never sure the guy i used to have the lpg serviced checked it and said he could find nothing wrong and t actually ran cleaner on lpg than petrol but he did say if it was fitted and a wire was not connected 100% then maybe it's that what is causing the issue

could be. this point am going with lambda sensors though. the lpg system has been looked over by 3 different lpg technicians.

bit of an update to this.

so I was messing about with the car trying to make it throw codes. I held 3k rpm for 30 seconds and it threw cylinder 1 misfire codes, lean codes and the reduced engine performance(ive already replaced sc coolant pump). So am like huh, how about that.

So I go change plugs and swap coils for that cylinder.

Same thing happens again, but still cylinder 1, I managed to replicate it a good 4-5 times. So I thought what if I run the car on lpg, then do the same, held the revs at 3k for a good minute or two. No misfires, still throws lean code but I've a feeling that's more adaptation/map related.

So for now I've come to conclusion injector 1 is clogged. Only thing that would explain it really. I remember seeing a service bulletin for it somewhere which recommended bg44k so I've ordered some of that

another update. it was the maf. i thought it was a denso maf that came with the car, wrong. it was a chinese one and the replacement chinese one i had was no better.

one denso maf later and all the lean codes went away.

now onto the next problem

edit: i havent run it on lpg since. i wanna get the lpg reducer and injectors swapped out and then a full recalibration now the fuel trims are somewhat sane

Hopefully sorted then