Vy LPG issue

[dodemach]

Hi fellow Commodore lovers,
I have a 2004 VY Equipe with factory/Dealer fitted LPG. While running on LPG it's fine apart from when I let off the accelorator and coast, the revs will drop below normal idle speed. It will sometime surge and jump up the revs again but will settle back and do the same again and sometimes it will stall and this can become quite unsafe as I try to start it again while rolling. If I slow and apply the brakes it seems to settle to normal idle speed ok and will idle happily while waiting for the lights to change. This only happens while on LPG, when I change to petrol it behaves perfectly. Is it a problem with the LPG system, a vacuum hose that's connected to the LPG system, or an o2 sensor issue, but my assumption on the o2 sensor would be that it would misbehave when on petrol as well.

Cheers to anybody that has some advice.

[strgas]

sounds like its leaning off on deccel and stalling the engine could be a number of things secondary diaphragm sticking or bleeding off pressure , have you checked the vacum hoses for leaks ? is the idle higher on petrol too ? any trouble codes or engine light coming on ? has the vehicle back fired recently ?

[dodemach]

sounds like its leaning off on deccel and stalling the engine could be a number of things secondary diaphragm sticking or bleeding off pressure , have you checked the vacum hoses for leaks ? is the idle higher on petrol too ? any trouble codes or engine light coming on ? has the vehicle back fired recently ?

Cheers strgas,
On petrol idle looks to be the same, around 650 rpm, I've checked the hoses for vacuum leaks but can't detect anything, all attached well and no splits or cracks. No engine codes show, only the Battery light when it's about to stall or stall altogether and no backfires recently.
It started doing this some time ago, but I adjusted the idle at the cable bracket, probably six months ago. This seemed to solve the issue well but when the condition started again I adjusted it more but then the car wouldn't start. I'm guessing this is because of the throttle position sensor.
The thing I'm wondering I guess is if there is a simple solution or it's time to take the car in for a gas tune, but the thing is it's running beautifully apart from this issue, doesn't miss a beat otherwise.

Thanks again.

[GenReaper]

yeah it will be a combination of TPS and closed throttle position.
Get it retuned.