Immobiliser & Running Problems - Please Help!

Hi all,

New to the forum and hoping to get some help...

I own a 1994 Discovery Series 1 - 3.9 V8 IS with an LPG conversion and have had a couple of problems of late...

1. The central locking / alarm / immobiliser has stopped functioning. It's the standard CATS system with a single button key fob. The batteries were replaced recently and the key fob is sending a strong signal (had this checked by the AA). However, returned to the vehicle the other day and the the key fob wouldn't operate. Got into the car using the key but the alarm went off and immobiliser was still immobilising!!! Managed to disconnect the siren (before I went deaf!) and bypassed the immobiliser by connecting a wire direct from the starter motor to the battery live to get it started. Still starting it this way but far from ideal!

2. I've also got issues with starting. Generally fires and runs first time, but sometimes won't fire at all. Usually gets going eventually, but been caught out once or twice! Checked all the usual and given it a service, including new plugs, leads, dizzy cap etc but no improvement. I think this might be linked to a general intermittent running problem where the revs drop and sometimes it stalls (running on petrol) with the opposite problem of sometimes the revs increasing to about 2000 when in park / neutral (it's an auto) running on LPG.

Getting slightly vexed by this now... Any help greatly appreciated. Thanks, Robbo.

check for a vacuum leak, choked fuel filter, tank vent/restricted fuel pipes.
ignition timing, loose conection in the ignition circuit. keeping it simple to start with.
could have something to do with the gas conversion, check all related wiring.
might even have something to do with the problems your haveing with the immobiliser.(guessing now)

Using the key to open the door will only open the door. You still have the car imobilised untill you use the keyfob. I don't have a solution to the alarm thing except finding the alarm and bypassing the imobiliser bit. This could cause problems with you'r insurance if they expect you to have an alarm...

Thanks for the tips folks.

Muddee - will check out what you've suggested and see if it makes a difference. Given that the problems occur running on either petrol or gas, I reckon it must be something that affects both fuel circuits, so will check out for a vacuum leak, or something on the ignition circuit. Could a weak coil cause these problems do you reckon?

James - managed to bypass the immobiliser so up and running again - thanks for the advice about insurance (hadn't considered that one!)

just out of interest where is the imobiliser unit?

The immobiliser unit is tucked under the dash on the driver's side. Kind of underneath the fuse box and behind the plastic trim covering the inside of the wing.