Hi, can anyone help?

We have a 50th Anniversay Defender which has a 4.0 V8 engine.

It has an LPG conversion.

On LPG it works fine, but if I switch over to petrol things start to go wrong.


The revs drop down to 0 and then it either stalls or it revs up to 1000, then it drops down to 0 again and revs to 1000 and so on. Sometime it does that for ages, soemtimes it cuts out as the revs drop.

As the revs fall the battery light comes on briefly and if it stalls stays on but if it revs up it goes out again.


We have spent almost £700 with out local garage trying to get this mended and now they have said it might be worth changing the ECU to see if that helps.

They are adopting a trial and error approach which is a little frustrating.

According to their computer - there is nothing wrong with the vehicle.

They reset the ECU, replaced the throttle switch and also the idle control valve but its exactly the same.


If its doing this bouncing rev thing and I switch it over to LPG - its fine again - revving at about 500rpm when idling. If I switch back to petrol it starts going it again.

Can anyone help?

Thanks

Anthony

Is it just a tick over problem on petrol or does it cut out if you swap it over when driving?

When driving it on petrol and it has one of these episodes does it rev up to a certain point, say 1500, then instantly cut back and wont go over it making extremely difficult to get up to speed?? If so I have the exact same issue and No one seems to be able to put their finger on it...
With the eliminating every possibility first, theory, it gets bloody expensive when garages are involved so Ive been trying to learn some bits on my own, taking the air filter off worked for a little while but then it started doing it again a little while later...
It takes the fun out of driving it because I'm constantly paranoid it'll brake down somewhere...

So I cant really help you but I can tell you you aint alone...Theres a few threads on this and I guarantee some smart arse will come and tell you to search it but Ill tell you now, there isnt one answer to it as far as I can tell...