mis-fire all the time except when LPG on VR6

[poofpaddy 0]

Please can anyone help with the following

 

I've got a misfire hot or cold, I've replaced the leads ,coil pack and plugs with NGK platnums.No different except when I switch over to LPG it runs much better with a very slight misfire but won't accelerate hard or tick over on deceleration.

 

Just done 160 miles no cheese in oil or water, no lose of water

 

Switch back to petrol from LPG ticks over and doesn't stall on deceleration but misfire bad

 

What next please

[v8rumbler 0]

LPG is very critical of ignition components . Once a car is set up for LPG everything needs to be spot on. Check your plugs- they s/b very clean as gas burns very cleanly. What leads are you using? They can make a big difference . Disco's and Rangy's only run well if Magnacor's are used.

Hope this helps

Darren

[jamiehamy 0]

Hmmm...usually it's the other way round with LPG being the highlighter of issues.

 

If it's multi point,the LPG takes the map from petrol, and if your petrol setup is not right, LPG will never properly either.

 

Two things i would suggest next:

 

Replace fuel filter and give a good top up with fuel and Redex followed with a good long run. If you've got a blocked filter then this will hopefully clear it and give the ECU a chance to get back to normal.

 

Find someone with VAGCOM and see if there are errors - very likely. MAF/Lambda/cam sensor could be duff ) for starters.

 

If it's affecting both fuels, it would appear to be a sensor that's gubbed.

 

When did the problems start? After the run, during, or gradually happened?

[poofpaddy 0]

From the minute you start it up from cold so all the way home

 

I'll have a go at the fuel filter tomorrow... don't mean to sound stupid but where is it located.More of an air cooled man. I'll obviously look under the car where there normally located.Think I might even have a fuel injection filter if the same from my fuel injected van.

 

Runs smoothly on LPG will sit at 80 all day long but won't accelerate hard

 

Switch it to petrol and then it runs lumpy like its missing

[jamiehamy 0]

In front of the rear drivers wheel.

 

I'd soak the bolts/screws in SuperCrack or something overnight because they'll probably be a pain to get off. Once off, it's easy.

 

Also an idea to take a spark plug out and have a check what it's like ( even after replacing). Sparkplugs.co.uk do a good guide as to what the condition means.

 

Sounds like under fuelling, which wil affect both fuels, cause stalls and lack of acceleration.

 

Is the LPG multipoint injection, or single point?

[Majik 0]

Assuming its a proper LPG conversion it'll be sequential injection running an emulator a device which (when running on LPG) basically fools the injector ecu to think that its still running whereas in fact the signal isnt going to the injectors because the LPG injectors are working. Switch back to petrol and the injector circuit is complete and the injectors are firing. Sounds like either the emulator components failed or a wire is broken. Check for broken wires or emulator box damage or if you can plug the injectors back to the original loom and see how it runs. As on VR6 the injectors are burried under the inlet manifold this would need to come off.

Hope this helps

[poofpaddy 0]

Not sure what LPG is fitted will investigate tomorrow

 

Just replaced fuel filter doesn't rev up any better without misfire but will give it a run tomorrow

 

Thanks everyone for your help

 

majik...that would make sense because if you come off a run approaching a roundabout and switch to petrol it runs and doesn't stall.If left on LPG its like it runs out of fuel.Once it stalls at lights or roundabout its a pig to restart and stinks of gas when it does restart and loads of white gas smelling smoke.

 

The emulator box would it be a non std black box mounted to bulk head with two plugs going into it...as its no longer mounted to bulk head and fallen in engine bay.Which is a s much as I can see at mo in dark

[poofpaddy 0]

Right I've replaced the fuel filter, put reddex in the fuel giving it a good hard run

 

Changed coil pack again for another brand new one - no change

 

misfire is worse at low revs above 3000 not so bad and flies

 

Doesn't stall and ticks over lovely on petrol

[v8rumbler 0]

How long has the LPG been in? Is the plug gap correct? What is the state of the plugs now .

[Majik 0]

The emulator box would it be a non std black box mounted to bulk head with two plugs going into it...as its no longer mounted to bulk head and fallen in engine bay.Which is a s much as I can see at mo in dark

It could well be but i doubt it, thats probably the main ecu for the lpg, the emulator box will have a wiring loom going to the injector area and i would assume it would be closer by, front panel area,

[poofpaddy 0]

Thanks very much everyone its not cured.

 

Went for another run today over to a mates garage and on route it cleared itself the Redex must of done the trick and new fule filter.

 

Put it on computer cleared any faults, re run on computer no faults found. Drive back was lovely and smooth on petrol and LPG...results :-)

 

Going to spend tomorrow replacing the heater matirx.

 

Just sunroof and spoiler to sort now.