1996 V8 on LPG lacks power at 70MPH

Hello,
I've just bought a 1996 3.9 V8 with a multi point LPG conversion. When I'm driving on the motorway I find that I do not have much power at 70mph, can anyone tell me if this is normal when running on lpg as I know there is less power than petrol. If I switch to petrol it is a bit better, but still not a great deal of overtaking power.
This is the first discovery I have owned and so I do not know what performance to expect when driving on the motorway... Any feedback regarding this would be much appreciated.

New member... drjones.

dunno if its any help but when my single point LPG V8i disco is running low on gas its supposed to switch over automatically to petrol however instead it loses power whenever i take it over 3000RPM, i just switch it over to petrol manualy and it runs fine, not sure about motorway performance yet but will be able to tell you in a couple of weeks after ive been on my holsMrJones

Thanks for the reply... I have found that when on lpg - even with full tank of gas - after 3000rpm i loose power, in any gear. Going to get the lpg serviced this week so that should identify any issues.

drjones...

well let me know when you find out as it may help me solve my minor LPG problem. Apparently especially with multipoints ive heard that you dont really notice the power decrease with LPG so i reckon you got a minor fault there somewhere, in my experience quite often a minor problem can present itself and cause you to think its gonna be something major, i have also heard quite often that unless your LPG system is running pretty perfect (leads/plugs etc) you will experience rough engine running problems. hope this help ya buddy

could be down to worn plugs,leads or a dirty air filter as lpg systems do not run very well if these items are not perfect! good lpg systems should work with not a lot of difference in performance to petrol when running right.

Hello, I bought a V8 LPG about a month ago and I can't tell the difference between gas and petrol other then a slight change in engine sound at high speeds. It's really subtle though. At 70 there isn't a lot of power in the old girl but it does pull up to 80 quite smoothly. Good luck.