GAS Prob's

Had a backfire and you have blown a vacum hose off somewhere
Check all your hoses

Hi tt, you will find it is drawing air as stated before from a popped hose or more likely if it has the long straight tube from the air cleaner to the mixer there are purpose holes there to absorb the explosion some times has a stubby holder around them, check that out & if so just twist it around to cover the hole or replace it (the stubby holder) not a repair you can't do - just find where it is sucking the air in. see ya

Normally I'd say it sounds like you blew up the MAF sensor (Mass Air flow sensor), but I think I've been hanging around fuel injected engines for too long.

In the case of the 3F engine, I'd agree with the others...Vacuum leak.

Easiest way to diagnose where exactly it's coming from, if it's not audibly obvious, is to spray small amounts of WD40/CRC around the area of the suspected leak. If the idle improves, then you've found the source.

Be careful not to spray the gear near a hot exhaust manifold.

Fixing it could be as simple as refitting the hose, pluging the hole or wraping a bit of old inner tube around the source and securring it with a band clamp or the like. Creativity is no boundry here....just be sure what you use won't get sucked in to the engine. You'd hate to give the ole girl heartburn.

Cant seem to find any air leaks at all

Where's the PCV valve on a Land Cruiser

karl

I used to have a dual fuel FJ62 that backfired through the carby a few times.
The gas bloke I used to take it to for repairs reckoned it was "blowing out the diaphragm in the gas mixer".
The only way to prevent it happening was to feed it new plugs, points, and leads every 6 months. That got old real quick, and threw the economic benefits of running on LPG out the window. The unreliability of the LPG, together with the loss of cargo space due to needing 2 gas tanks to get any sort of a worthwhile range out of it, saw me trading it in on a diesel troopy. Never looked back.

The fact that yours "runs on fuel OK and does idle" suggests to me that perhaps it has not been tuned properly to run on LPG....mine could be tuned to run sweetly on either gas (but poorly on petrol), or petrol (but poorly on LPG), but never both :-(

Good luck getting it sorted.

Cheers
Glenn