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[BC]

I have a 2000 2.5 V6 CDX fitted with a Necam Coltec LPG system. It's been excelleny until last week when there apeared a serious loss in power when trying to accelerate. It's fine driving normally but the power is well down. I have also noticed a rather loud hiss coming from somewhere under the boot area. Again this only appears when accelerating hard or climbing hills. The LPG tank is in the boot but it is definately not an LPG leak. Anyone got any ideas what's going on?

Cheers

BC

[JamesV6CDX]

I seem to recall the Koltec systems had a pump in the tank - which when went, was a nightmare?  :-/

[JamesV6CDX]

I would get it hooked up to some software and check the gas pressure, for starters

[Lazydocker]

go here and search for koltec/necam or vauxhall. It's a very handy site full of some very knowledgeable people, a bit like here really, and I'm fairly sure I've seen this topic covered there.

If I get a chance tonight I'll have a hunt for the exact post for you

[BC]

Many thanks all.

It now seems the hissing is coming out the exhaust tailpipe, it is very noticable when the car is idling cold. First step is a visit to an LPG doctor I think.

Cheers

BC

[omegod]

I have a 3.0 v6 with a Necam system, It had similar issues and seemed to be misfiring when on gas, I had trouble finding anyone to touch it as they can be tricky apparently.

I eventually tracked down the installers, Northern autogas in Heckmondwyke? who changed the filters and it was resolved for about £100. Would obtain the filters and do it  myself next time tho.

Hiss from the rear may be a holed silencer!

Good luck

[Lazydocker]

The Koltec/Necam system is very sensitive to coolant level, flow and temperature. But it may just be that it's due a service

[BC]

Hi again.

I think I can rule out the LPG as it does the same on petrol with the gas fully isolated. As mentioned the hiss sounds like its coming out the end of the exhaust where I would expect the mucky stuff to emerge, not a leak. The hiss is loud enough that when the engine's under load that you can hear it inside the car even at motorway speeds, ease off the throttle it reduces. Just a thought but could a failed/damaged cat cause this?

Cheers

BC

[Entwood]

I wonder if your rear box is failing and blocking with wadding, so giving back pressure causing the hissing noise.

On the old miggy that happened and power was badly affected.. but I found the problem when all this wire wool like stuff started coming out of the exhaust pipe !!!

New rear box sorted it. I'd try getting someone to rev the engine while you feel the exhaust gases .. should be really free flowing .. or disconnect the rear box and see if it improves

[JamesV6CDX]

I wonder if your rear box is failing and blocking with wadding, so giving back pressure causing the hissing noise.

On the old miggy that happened and power was badly affected.. but I found the problem when all this wire wool like stuff started coming out of the exhaust pipe !!!

New rear box sorted it. I'd try getting someone to rev the engine while you feel the exhaust gases .. should be really free flowing .. or disconnect the rear box and see if it improves

Fully agree

My old 3.0 would hiss like mad - the exhaust was full of horse-hair wadding...

New exhaust (Ok, I cut the backbox off    ) and it was as good as new  

[JamesV6CDX]

I wonder if your rear box is failing and blocking with wadding, so giving back pressure causing the hissing noise.

On the old miggy that happened and power was badly affected.. but I found the problem when all this wire wool like stuff started coming out of the exhaust pipe !!!

New rear box sorted it. I'd try getting someone to rev the engine while you feel the exhaust gases .. should be really free flowing .. or disconnect the rear box and see if it improves

.

Stick a rubber glove over the tailpipe and see how quickly it inflates