My EL is running ok on LPG, but on petrol it idles up to 3000rpm.

I gave the idle speed controller a decent clean as per this page http://www.fordmods.com/documents.php?d=23. It's still black inside, but it had a good wash with both turps and WD-40. Reassembled it all and nothing has changed. Still idling like a Saturn rocket.

I found that by disconnecting the MAP sensor the idle revs would drop a bit, but still too high. When I disconnected the ISC wire at the same time as the MAP sensor is disconnected the revs drop a bit more, and its nearly tolerable, but still too high (~1200rpm). I'd consider running it with both disconnected, but it conks out on LPG with teh MAP sensor disconnected.

I've turned the idle screw to the extent that it's lost contact with the lever, so it can't be that...

Any tips would be hugely appreciated. I'm flat broke so trying to avoid a trip to the mechanic.

Cheers,
Scott.

I would be looking at a vacuum leak at the inlet manifold gasket, hoses of the inlet manifold etc...

+1 for Vac leak

This is what I keep coming back to, but I've checked and doubechecked all the hoses and everything seems connected, no splits in hoses etc.

I noticed that down at the front some of the air filter box clips are missing and there's not a tight seal on the air filter box, but I don't think this would be the cause, would it? It doesn't seem to improve when I manually force a tight seal on the air filter box.

check for a busted pcv valve, sometimes the plasic pcv's fail causing a higher idle and symptoms of a vac leak...