O2 sensor reading 0V because a cylinder was misfiring (as you said it was running rough) and the fuel trims weren't moving because they couldn't move any further.

Glad we got to a conclusion, I've got a ferry to Calais to catch in 3 hours.......

blueplasticsoulman wrote:

So if i understand correctly.....

The fuel trims learn the petrol side. If then it switches over to gas, it then has to relearn for the gas. then it switches back to petrol and so on and so forth. each time trying to relearn whats going on.

No, it learns on petrol and the gas system SHOULD be set so it doesn't know it isn't running on petrol, the injector pulses should remain the same and the lambda readings should remain the same so it doesn't have to relearn. Only when the gas system is out will it relearn and cock things up.

It will sort itself out fairly quickly with a bit of varied driving, a mix of low and high speed with acceleration and deceleration in between is ideal.

You have proved your LPG system needs calibrating. By driving it around on petrol only you have allowed the long term fuel trims to adjust and get themselves correct for running on petrol again. As soon as you changed to gas they should not change at all, they should stay exactly as they are but they aren't doing as the gas system isn't calibrated correctly.

Lets say for arguments sake that at a particular revs, load and throttle opening, your petrol injectors need to be open for 10mS but on gas, as the injectors don't react as quickly and you are injecting a vapour not a liquid, the LPG injectors need to be open for 14mS. In that case the calibration in the LPG controller will be set to add 4mS to the pulses from the petrol ECU (which are intercepted and used to fire the LPG injectors instead). However, if it is only adding 2mS the mixture will be lean, the lambda sensors will tell the petrol ECU that it is lean so it will adjust the pulses to 12mS. So the 12+2 gives the required 14mS. Then when you go back to petrol, the pulses are still at 12mS which is too long and the mixture is running rich. If one of your plugs or leads is a bit iffy the rich mixture causes a misfire. The unburnt air from the cylinder that isn't firing makes the lambda sensor see too much air so the petrol ECU thinks it is still too lean so richens it further and the downward spiral starts until it is in the state that yours was in. Resetting the adaptive values would have done the job at the press of a button but without anything to do that with, you've had to let the ECU learn for itself.

Get it booked in to get the LPG system properly calibrated.

There's a problem somewhere but without having it in front of us it's all theory and speculation. The P1319 code is misfire at low fuel level so that suggests you do have a misfire so it could be the misfire that is causing the apparent lean running. In all honesty, you might be best getting Simon to have a look at it. Far easier to diagnose a problem when you can see it for yourself.

You've gone awfully quiet Mark, haven't you got those new heads on yet? What's the state of things at the moment?

blueplasticsoulman wrote:

You should be able to view the trims in Torque - What are they showing? Both banks and long and short term?

Already done. Read full topic for back story.

No you haven't. You've said if they are moving or not but not what the actual values are. I suspect your long term trim on bank 2 is going to be hard over to positive making it rich.

Yes, 0V is showing a lean mixture, i.e. too much oxygen in the exhaust. If that was down to an air leak in the intake you'd have a stupidly high idle and if it was down to an air leak in the exhaust before the lambda sensor, you'd hear it. Equally, if one cylinder on that bank isn't firing the air drawn in for that cylinder would go straight out of the exhaust and make it think it was lean even though the other 3 cylinders could be spot on. Then when it corrects by bunging more fuel in, the other 3 are running ridiculously rich but the sensor is still seeing too much oxygen making the ECU think it is still running lean.

You can check continuity to the sensors with a meter. There would be continuity from the blue and red/black wires you have already found at the ECU, there is also the white/orange wire which also goes to the ECU. The ignition switched 12V supply comes directly from fuse 26 (not 28 as I said earlier, I need better reading glasses) on a Brown/Pink wire. You have a matching set of wires to the LH sensor, a red/black, white/orange and brown/pink which all go to adjacent pins at the ECU, the only difference is that the LH sensor signal wire is orange rather than blue.

But can Torque reset the adaptive values? That would reset the trims to base settings. A normal code reader can't, the only thing I know that can is a dedicated diagnostic tool such as a Nanocom, Lynx, Tesbook, etc.

Yup, that's a modern sequential system and not something really horrible like an Etagas. I'm wondering if Torque is telling the truth and you really don't have anything from the lambda sensor or if it isn't showing it. I say that as the trims altered under acceleration yet the lambda output didn't. With no lambda signal the trims wouldn't move, they'd be stuck hard over one way and not at zero.

Yes, the heat shrinked black wires in teh first picture are a bunch of earths all connected together. You've got two pairs of screened wires in teh second pic, one with a blue and red/black which goes to the RH bank lambda sensors, the other one is an orange paired with a red/black. These are screened so the bit you can see in the third pic is the screening. Each of those are paired with a White/Orange (which you can see coming out of the connector in the last pic) and a Brown/Pink that comes direct from Fuse 28.

However what isn't there is anything tapped into it for the LPG system......

On a Thor, nothing. That's where the ECU lives on a GEMS and for some unknown reason they left it in on the Thor. People often use it to keep jump leads, spare sandwiches or an LPG ECU. If there's wires coming out of it, I would suspect that's where the LPG ECU is living.

blueplasticsoulman wrote:

Do the O2 sensors tell the LPG to turn on when it's up to temperture?

No, the LPG turns on when a temperature sensor on the reducer tells the controller it's up to temperature. The O2 sensors don't have anything to do with the LPG system, they are talking to the petrol system and the LPG system is slaved off that. Without a connection from at least one of the O2 sensors, when setting up the LPG system you need to be looking at a live code reader (to see what the O2 sensors are reporting) and the LPG software on a laptop. With the connection the LPG software will display the O2 sensor outputs so all the information is in one place. That's the only reason for the connection so disconnecting it won't affect how either system works (or shouldn't if they aren't arguing with each other).

If it's been done properly, the extra wiring should be made to look like it's part of the car. No idea how to get the ECU out on a Thor, I've got a GEMS and you don't need to lift it out, the connections are all on the top. But this is what RAVE says

Sounds a little bit raspy to me, you need larger bore pipe to get it to rumble. Bit late now though.......

That's the one. You shouldn't need to wiggle it out if you are just looking for extra wires tapped into the ECU wiring. They should be fairly obvious as being extras.

This guy had exactly the same problem on a Thor fitted with a Prins LPG system https://rangerovers.pub/topic/354-02-sensor-voltage-fixed-low

It might but it depends on the exact LPG system you've got. Worth a try though.

There will likely be a feed from one of the O2 sensors to the LPG controller. It'll likely be a purple wire and be connected in the petrol ECU box. Disconnect it. The LPG system doesn't need it, it's there so you can monitor the lambda sensor output on the LPG software but it isn't unknown for a stray voltage from the LPG system to confuse the petrol ECU. Output signal from the RH bank sensor arrives at the petrol ECU on pin 16 of C0635 (24 pin black plug) on a blue wire so you will be looking for something tee'd into that.

I was once helping a mate fit the exhaust to a kit car that used a Ford V6 Essex engine. He'd got a set of tubular manifolds but the engine was converted to dry sump so the manifold hung down much too low so had to be modded. After cutting lumps out of it, we tried to tack weld it in place and then remove it to weld it properly but couldn't get in there easily to tack weld. Then we had a brilliant idea, Superglue it together in situ then take it off and seam weld it on the bench. Not such a good idea, the Cyanide fumes from hot Superglue damn near gassed the pair of us.....

That will do the job nicely and will bolt straight on in place of yours. The only difference I've seen between odd ones is the position of the output speed sensor. On some it's on the top on others on the side. Not important as the cable will reach either way.

Good point, as it's showing heater faults on both sensors. They are both powered from fuse 28 in the engine bay fuse box. Although even if it was a heater circuit failure, there would still be a reading from the sensor once the exhaust had warmed it up which is why I suggested swapping them over to make sure the fault swaps banks.