I have a 130,000 mile D2 auto with multipoint LPG. symptoms are:

1) When starting from stone cold (on petrol) it starts and idles perfectly.

2) If you then try to drive it pops, bangs and nearly dies. Just possible to drive. Smooths out above 2000rpm.

3) When it switches to gas (<1 mile), it is still a bit rough under 2,000rpm.

4) Once warmed up it drives fine on gas and is lovely and smooth. That said it seems it's 'economy' is less than it should be and it is not all that quick. A friend has a P38 4.6 on gas which will do 16mpg in general driving and up to 22mpg sitting on the motorway. Well, it appears my Disco will only do 12mpg and is only being driven gently.

5) If I switch to petrol when it is warm (tank nearly full of fresh petrol), it is much rougher than on gas and does not feel quite 'right'.

My friend with the P38 says that much of the LPG system is piggy backed off the petrol systems so I must "get the petrol side right first".

I have some Forte injector cleaner to run through ... a good idea on LPG cars where the petrol injectors are not used much but not, I think, the root of the problem.

Leads and plugs are relatively new.

My main concern is not to waste cash. I have read many threads where just about every component is changed before the guilty component is found!

Does it sound reasonable to get fault codes read first? If so, what machine do I have to check my local indie possess?

Second, has anybody here found, and cured, a smilar fault and have a good idea what might be wrong? I am starting to suspect the ECU from what I have been able to read.

Sounds like an ignition fault, possibly a lead or coil pack. Although generally petrol is more forgiving than LPG for slight ignition problems.

I get 12ish around town and 16 on motorway at 60, 12ish at 70 with my D2, and that's just hit 134k today.

Ben

Thanks for the mpg figures Ben. My motorway work has been at 70mph so perhaps it is giving about the right 'economy'! I had expected about 15mpg on gas but mileage will only be about 3-4000 a year so no biggie ..

I would love it to only be a coil pack! Like you say though, it is the petrol side that is worst!

Would you agree I need to get the codes read before buying anything?

Getting it on testbook should tell you what's wrong with it. It will tell you what's misfiring and from that you can tell if its a coil as a pair will be missing together. If it's one then look to lead or plug, but whoever puts it on testbook should be able to help with interpreting that to an actual fault.

probably temp sensor for ecu to let car know if extra fuel is neede for cold running like automatic choke

Thanks for both replies above - most helpful.

I am going to visit my local LR indie this afternoon to see what sort of outfit they are. If they seem OK, and have testbook, I will book it in for a code reading and take it from there.

Solved

The technician at my local LR indie first checked the emissions - sky high! He then looked at the plugs - in a poor state, especially on bank 2. They were new a few thousand miles ago. So, on with Testbook which showed a lamda sensor out. Looking at the bad plugs and playing with a multimeter proved it was the bank 2 sensor. The good news is they are only £47 each. The bad news is they are a pig to get out and fit and I ended up with 3.75 hours of labour on the bill. In fairness, I did ask for a once over of the whole vehicle as it is new to me so that accounts for some of it.

£370 was the total damage which includes new plugs and the inspection. My only gripe is that they have obviously used the world's most expensive spark plugs and I understand that LPG is happiest on cheapy ones. I now wish I had given them a set of 8 to fit - would have saved me £50 I reckon

As soon as I pulled away on petrol, I could feel the difference - smooth and pokey! It went straight to gas so I reselected petrol for a short bit and it runs sweet. Gas now feels about the same as petrol which sounds about right. I assume it will now do better than 12mpg - maybe the dizzying heights of 15? :lol:

Of course, I cannot verify the cold running till tomorrow but I am feeling pretty certain that all will be fine.

A rather nasty bill only 3 weeks into my ownership but driving home with the (only working) sunroof open and the window down and the V8 purring felt rather good.

Till SWMBO asked what the bill was ........... :doh:

I changed both the lambda sensors on mine a year or so ago as I had the mil light coming on a fair bit. I had originally put a cheap one on. But it made no difference so I got proper Bosch ones and it was fine.

I dont remember it being difficult though. A couple of mins on the sensor but the plug was maybe a few more as that's a little difficult to get at lying on the ground, I expect a ramp would have made it easier.

I know on my wifes d1 it was a lot harder as the old sensor would not come out so had to get a new boss welded on so I could put the new one in.

AIUI, it's all to do with whether the lamda will come out or not - mine involved tapping and dieing I think, from what he says.

The good news is that I started it from cold this morning and it shot up the road like any normal vehicle

I am poorer but happier!!

Glad it's all worked out for you. Happy motoring