I have an EA I6 MPFI Manual on LPG.

Now when I have the ISC connected it runs really rough on both LPG and petrol but if its disconnected it idles and runs great on LPG but wont even think about running or idling on petrol. I have even put a blanker plate on the ISC so it has no effect and yet it still does the same thing.

Does the ISC effect timing in any way?? as that is the only thing I can think of that would cause this.

idle with the ISC connected runs like its got a hot cam in it, tried changing timing but makes it run worse.

it could be a dirty ISC
have u cleaned it?

also how old are plugs/leads and also the dizzy cap/rotor

this is one of those of the wall things,
OK I will try and explain what is happening. With the ISC disconnected on LPG it runs perfect but will not run petrol. you can sit on about 2500 rpm do the changeover and it just dies.

with the isc connected (it has a blanker plate put in so it should have NO effect it runs like crap on LPG (like its dropping cylinders) but you can do the changeover at 800 rpm and do the changeover and it runs on petrol and that too runs like crap.

so in the end I either have it disconnected and it runs perfect on LPG or I connect the ISC and it runs like crap on both.
I always like the idea of duel fuel because of the backup factor.