Running well on LPG but badly on Petrol?

[paulmmc]

My 1987 3.5 V8 EFi rangie runs really nicely on LPG but doesn't idle at all when switched over to petrol. It does start on petrol and drives so long as i keep the revs up but as soon as i take my foot off the accelerator when running on petrol the revs drop really low (about 200rpm) before cutting out. All's well when running on LPG. Any ideas what I should be checking?
I'm new to fuel injection as always ran carbs before so any advice would be great while i am waiting for the Haynes manual which is winging its way to me as i type.
Thanks,
Merry Xmas

[Range Rover Blues]

If it's a single point system (which I suspect it will be) then the LPG system is totally separate.

What we can deduce is that your spark is fine, LPG is harder to burn that petrol.

Check the timing hasn't been over advanced to suite LPG though :!:

So what you've got is basically a 3.5 that runs rough, it has a fuel problem.

Get the haynes manual, it's not too bad on EFi stuff.  I'm suspecting there is a problem with the idle settings and I'll bet someone has a**ed aropund with the throttle plate to get the LPG system to idle smoothly.