Alright another big day today.

Sitting down with a mate at the pub we were talking about my car and how LPG is practical and economical on such a big V8.

As you recall everything on the car works fine until it gets to about 95C,and then only o2 voltage drops, and it smells of petrol etc etc

And at some point my friend said "only thing that bugs me with LPG is that you have to start on petrol, let it heat up and then you can switch to Lpg"

And I had a House MD light bulb illumination moment. We disconnected the red and black wires of the lpg system from the battery positive and negative, started the car (already up to temperature) and instantly both 02 sensors started fluctuating as they should, and the strong petrol smell disappeared instantly.

We reset the adaptive values and went for a drive.

Problem solved !!

Well, not completely, but at least now we know that it's when the LPG becomes available that something happens that causes the signal to crash. Probably something to do with the emulators or the wiring... But that's for later

I'm so happy

Thank you all, great forum and great people !

What LPG system have you got? Mention of emulators would suggest either a singlepoint or Prins as most other systems don't use emulators. However, if you've got a singlepoint, you don't need to let it warm up on petrol, it'll run on LPG from the word go. I've still got petrol in the tank that I bought in Latvia in September last year.

As Gilbert says.

Also, there are various kinds of emulators with the two most common types being petrol injector emulators (dummy electrical load to simulate petrol injector electrical load) and lambda signal emulators. You don't usually need a discrete pinj emulator with a sequential LPG system because one is usually built into the sequential LPG ECU (except on a minority of systems such as Prins / AG as Gilbert says), and in fact you don't really need a pinj emulator at all on a Rover V8, but it is best to fit one. Sequential systems don't need to emulate lambda because they work as a slave to the petrol system so the petrol system's closed loop operation continues to work as normal (if LPG system is in good working order and calibrated properly). If you have a single point LPG system (or any LPG system that doesn't work as a slave to the petrol system) then petrol fuel trims will drift when running on LPG unless a special type of lambda emulator is fitted, this special type connects to the vehicle OBD to monitor fuel trims and connects to the petrol ECU's lambda input so they can adjust the lambda signal that the petrol ECU reads, they then steer fuel trims to zero, thus preventing the type of fuel trim drift problems your post might describe. But since P38 OBD is none standard it can be difficult to find an intelligent fuel trim steering type of emulator to work on a P38, and since P38s don't kick up much of a fuss (no MIL light to show fuel trim errors etc), intelligent fuel trim steering lambda emulators are seldom fitted on P38s that could benefit from them. Single point LPG systems usually have facility for some basic lambda emulation but this isn't usually capable of reading OBD fuel trims, so it can't steer fuel trims to zero, in effect they just send an oscillating voltage to the petrol ECU (which can help on vehicles which come up with a lambda error if the petrol ECU doesn't see lambda voltage flick). This also isn't much use on a P38,so where P38s are converted with single point technology the LPG system often taps into lambda voltage so it can correct mixture while running on LPG, but the lambda signal that the petrol ECU sees is just actual lambda voltage, not emulated at all.

Simon

Hey,

Got a Prins Vsi multipoint injected system.

I have to let it warm before being able to switch over.

No lpg for now, I'm just happy to be driving again ! Yeeew