engine running problems

hi ive got a disco 2 v8 2000 on lpg dream system, the cars been running rubish for a while so put it on computer, it said faulty cam sensor/ timing and lambda senor on left bank no reading, i changed the cam sensor, and fitted a secondhand front pipe with cats and sensors, its only got pre cat ones fitted, ive run the car perfect for just over a week on petrol only with some injector cleaner as adviced by my local landy garage, last night on my way home i put it on lpg, and straight away the car was running all jumpy again with a big loss of power and no throttle response, i switch back to petrol and it ran brill again. this morning i tried lpg again the same happened so swiched back to petrol, but this time its not running right on petrol, all day its been a bit jumpy and lacking low end power, any ideas on whats happening, its starting to do my head in now, one thing after another, cheers phil

I had a RR on LPG when they run properly brilliant but oh dear if anything is out of tune, the LPG system relies on everything being perfect, alter something and it plays up, timing has to be perfect, all electrical parts linked to the ignition and running of the engine must be right. I sold my RR after a couple of expensive years, the LPG system left a nasty taste I will never use it again.

lpg requires good spark, so i would look at the plugs, leads and coil for that side of the engie

When running LPG it will need to be set up also, get the software and interface cable and learn how to set it up.

You must have an excellent well maintained system when using LPG if not you will be chasing your tail forever more.

I would say that it needs the LPG ecu tuning up, have you had the battery off at any point recently, it shouldn't but could reset the LPG ecu.


Also, the car ecu will make corrections to the fuelling based on the lambda, maf and crank etc sensors reading even whilst it is on LPG. The LPG system turns off the petrol injectors and emulates a return signal from them so as not to upset the petrol ecu and throw faults. So if the sensors call for more or less fuel, the petrol ecu will respond and put in fuel, or so it thinks. then when back on petrol the setting are wrong.

For this reason you need to set up the LPG system correctly so it is running perfect and it will then give similar reading as when on petrol. That way there is no marked difference between the fuels as far as the petrol ecu is concerned and it won't be making silly corrections?

Do plenty of reading. I learned a lot from LPG and would go back to LPG if the right car came my way. It's a very satisfying situation to have the v8 and cheap fuel.

So far, I've changed, the cats, lambda sensors, cam sensor, throttle sensor, maf, plugs, leads, coil packs and air filter, I've got software for gas ecu, the problem is the car goes dead when driving, it will always tick over, its that bad at times the car will not move at all, its an auto and will not even drive in 1st, as soon as the engine in under load it dies, then it will be ok for a few miles ans then back to the same, I've put a timing light on cylinders 7 and 8 and drove down the road but even though the car would not pull away and died, the lights flashed like a normal engine, I put a multimeter across the lpg solenoid which pulses the same as the petrol injector and the voltage is reading 2.5 volts, I was expecting it to be 12 volts, the car does the same on petrol or gas