Hey, I have a 2000 AUII falcon which shifts very weirdly under WOT (but only on gas). On petrol it shifts quite smooth and well under full throttle, but when on gas just when auto shifts gears it feels like there is a spark/fuel cut or something (you jerk forward as for some reason the engine stops producing power) then about a second later bang full throttle again... this can happen once or twice per gear change but seems to happen quite consistently.

The trans has just been given a normal service (just the 4L in the sump) i'm going to wait a few thousand kms before I do a full flush (I don't know the service history - just purchased the car) but the fluid wasn't burnt or overly dirty (it was a clear light brown and still had the ATF smell) there was a bit of metal in the bottom of the pan, but not what i'd say would be heaps...

As it doesn't happen on petrol i'd assume this would be an engine problem rather than a gearbox problem but any input would be appreciated. One last thing, it seems to run fairly rich on petrol (smoke coming out of exhaust) don't know if this is normal but anyway.

Thanks, Thomas.

I think you have answered you own problem.....

Under WOT on LPG above 4000rpm the LPG leans out on most occasions so the car stops producing power... I had this on my BA also when i first got it, go to overtake auto would chuck down a gear hit the wall at 4500 and would not accelerate, had to lift off (changed up) put foot into it again....

O2 sensor was iffy on mine.... does yours have a stepper motor controlling the LPG???

Yeah, looking at O2 sensor soon - it'll probably need to be replaced. Yes the lpg system does have a stepper controlling the mixture. I take it this is more likely to lean out at greater power levels?

Thanks, Thomas.

dud O2 sensor will really show up more while running on LPG....

One of the first things I replace as part of my 1st service when ever I get a car....

Well I can get >500kms to a tank on lpg which I have heard is excellent (but it is mostly highway driving). Where is the best place to get an O2 sensor, ripco and the like are all over $100... I can get one on ebay for ~$50 are they worth it?

Thanks, Thomas.

I usually get mine from Sprint Auto Parts, they sell genuine Bosch ones for $70 with the right plug on them....

If anyone is interested, the problem was the gas ecu changes from gas-petrol at ~4800rpm whilst transmission shifts at 5000rpm - then once it shifted it'd change from petrol-gas.

thats a strange one... never heard of lpg to petrol switchover under high revs before....

IS this a Vapour setup???

Yes, vapour mixer ring by "Motogas". I can find very little information on the supplier, controller is a mogas stag 100 (I think - will confirm later) which again, can't find info on. The switchover is solely dependant on rpm, ie it will switch over in neutral/park if I rev it above ~4800rpm.

Edit: it appears to be this: http://autogas-lpg.co.uk/conversion-kit/133-ac-stag-100-mixer-system.html

Edit2: I have found a manual for the controller, it has a value that sets the changeover rpm so when I get home today i'll connect up my laptop and using the program change this value.

Edit 3: Anyone know where I can buy an interface cable cheap for one of these/know if it uses a standard 8 pin quick disconnect (it looks like one) and if they do what is the wiring diagram for it.

http://autogas-lpg.co.uk/autogas-lpg-in ... togaz.html

from the supplier.....

I saw that, but thats $50 plus postage for just a cable (the software is free). I was wondering if there was anything that will be cheaper.

Thanks, Thomas.