Commodore lpg depression

YOUR problem is not unusual and there are several possible causes: fuel, ignition or engine wear. First, make sure the ignition is set correctly and it's not a bad idea to close up the spark-plug gap a little when you do that. It's also worth having a leak-down test on the engine, which will show up a leaking valve or worn valve stem seals. I'm guessing your engine has done plenty of kilometres and wear could be causing your problem.