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Some interesting posts there...

I get 16 mpg around town and 18 - 22 mpg on motorway, to get 22 tho its around 60 -70mph all the time, above that it goes down.

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round town mpg is not a good comparison as there are too many variables. outside temp, traffic lights, acceleration, heater, aircon, demister lights etc.

My MPG is down about 15% on LPG at around 24mpg, I find mine is within a few MPG when I do long runs but I was doing W Yorks to London twice a week so fairly easy to get some consistency.

I was getting warning lights (Lean on left bank) triggered on switch over, cured by increasing the switchover temp by my installer.

- could it be a small leak? have you tried filling and using quickly and seeing if mpg improves?

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I have often filled with LPG at one end of the country (say Cardiff) and driven home at 75mph and filled at the last LPG station before home, and never had better than 21mpg.

Mike

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yes fill and do a 100mile run, take it easy like 60 - 70 mph and i get 22mpg, 80mph and its 17mpg.

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Just did the Cardiff trip again yesterday Went down on LPG and got 20.9mpg came back on petrol and got 29.8 mpg

That's 30% worse on LPG. And we have tried everything to fix this. Anyone know what parts of the Romano system that I have got would be useable if I got someone to change the injector end to a different system - and if so which system?

Thanks

Mike

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Ok - now I am at a complete dead end. My guy has exhausted all possibilities and I've still got the engine warning light on and 30% worse fuel consumption on gas than if I switch to petrol. He has had Edward of Mint LPG up from Newport (the importers of the kit) who is now saying some cars are just like that and there's nothing more that can be done.

Any suggestions anyone? Ideally I would like to find someone who can sort it. Failing that I may press my fitter and/or Mint LPG to uninstall the kit and give me a refund - but it will leave my car with a stupid hole in the panel.

Mike

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Ok - now I am at a complete dead end. My guy has exhausted all possibilities and I've still got the engine warning light on and 30% worse fuel consumption on gas than if I switch to petrol. He has had Edward of Mint LPG up from Newport (the importers of the kit) who is now saying some cars are just like that and there's nothing more that can be done.

Any suggestions anyone? Ideally I would like to find someone who can sort it. Failing that I may press my fitter and/or Mint LPG to uninstall the kit and give me a refund - but it will leave my car with a stupid hole in the panel.

Mike

Failing that I may press my fitter and/or Mint LPG to uninstall the kit and give me a refund The only way to go.

Profess gas in southwales.

Mike

PS Ring Profess tell them which system has been fitted and the problem you have and lets see what they say.

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These V8 s do use a lot of fuel, they got 8 cylinders to be fed with fuel all the time, not 6 or 4. Gas is not as dense as petrol so will use more, mine i can only get 22mpg on gas is keep tp 55-60mph, soon as travelling at 70mph its down to 17mpg and above 70mph it only goes down....

Injectors can vary alot and cause less mpg, trouble is they are not cheap, even the not so good ones... just have to drive very steady....

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yes but if you read the thread, the fitters own car (which I borrowed) was returning much better mpg on lpg. His car is an identical LS430. He even swapped the injectors from his to mine to see if that would work. Also my engine warning light is almost always on. Lexus think that means the ECU is switching it to default mode because it doesn't understand the readings it's picking up after the CAT. If this is true it is making me wonder whether default mode is very rich - hence the poor mpg, but whether it will damage anything long term.

Mike

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Wow Mike, this sounds even worse than my saga, here

One thing that has suprised me is that there seems to be no way of working out what these engines are actually doing in real time by plugging into the ECU. Does any car have such a facility? Why does it seem to be trial and error? The worst culprit in my eyes was the Lexus dealer who were totally clutching at straws telling me the car was 'coked up'. I really expected them to be able to fix my problem.

Good luck anyway.

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Update - my guy invested in a new piece of electronic code reading analysis kit as he'd seen on their website a guy clearing the VSC code on an LS430. And it worked.

Another LPG company I contacted was very helpful even though they don't fit Romano. He said they have had problems with the LS's air flow meter triggering the engine warning light on LPG but not on petrol, so he suggested my guy swapped that from his LS to mine, which he did last night. We await results.

I think the other LPG company deserves a mention since he spent half an hour on the phone to me - they are Autogas 2000 Limited Carlton Miniott, Thirsk, North Yorkshire, YO7 4NJ Tel: 01845 523213 .... by the way this guy was honest enough to say that any LPG installation is going to be 20% worse than consumption on petrol - me I would be happy with that as mine is currently over 30% worse.

Mike

PS just looked up energy per litre for petrol and LPG and they are respectively 34.2 and 25.3. By my calcs that makes LPG 26% less efficient per litre than petrol, so maybe my 30% is what everyone is REALLY getting.

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Hi Mike,

I've followed your posts with interest. I'm on my third LPG powered car spanning over 10 years, 2 Ford Scorpio Cosworths and my LS430. The Scorpios I converted myself but when it came to the LS I decided that Profess Autogas in Cardiff were the boys to do it. Never had any issues with the Scorpios and I'm delighted to say that after a year I've never had any issues with the LS either. I get the money equivalent of 35 - 40 to the gallon and never really try to calculate the town and motorway mpg. I would recommend a chat with these guys and potentially a trip down to see them. I'm sure they will be happy to help you.

HTH

Tc

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Hi Mike,

Was browsing the web last night and stumbled across your thread whilst trying to locate myself a gs300 mk1 , i am a technician and former mitsubishi senior tech , have had some expirence with lpg whilst at mitsubishi way back, we had some concerns with dtc`s being stored various software rewrites were released to no avail , in the end it turned out to be to do with the engines valve seats , which required the valve clearences to be corrected , this was causing the hegos to register faults , im not sure if your car has hardened valve seats or not but some mitsubishi`s didnt , i previously worked with a polish technician at toyota , in poland lpg is very common and he said valve seat were a big problem, adjustment was carried out on most services on toyotas where applicable , we have had some security (high mileage) vehicle fitted with lpg which have burnt out the valves , if the clearence is to tight the valve over heats as the valve seat cools the valve through convection , when it is shut if its to tight the valve does not seat properly and cool enough eventually leading to a burnt valve, hope this is food for thought.

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hmmmmm ... what are the first symptoms of burning out valves. he fitted a flashlube (?) kit for me.

It's done about 8000 miles since the conversion and seems to be running fine.

Mike

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Hi Mike,

the concerns with engine lights coming on were the first signs of the valve clearence issue but we didnt know it at the time the car seemed to run ok but after the valve adjustment the fault did not re occur for quite some time but would reoccur due to the engine not having hardened valve seats maybe its worth doing some investigation as to weather your car has or has not, the kit your man fitted is designed to combat this , as for valves burning out misfire could occur , harder to start from cold and eventually loss of compression , wet or dry test would return the same compression result pointing to a valve train fault and not the piston rings , hope this helps and good luck in finding the cause .

PS Is the engine fault code related to the hegos (heated exhaust gas oxygen sensors). toyota refer to oxygen sensora as air flow sensors not to be mistaken with maf or map sensors.

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Hi Mike,

the concerns with engine lights coming on were the first signs of the valve clearence issue but we didnt know it at the time the car seemed to run ok but after the valve adjustment the fault did not re occur for quite some time but would reoccur due to the engine not having hardened valve seats maybe its worth doing some investigation as to weather your car has or has not, the kit your man fitted is designed to combat this , as for valves burning out misfire could occur , harder to start from cold and eventually loss of compression , wet or dry test would return the same compression result pointing to a valve train fault and not the piston rings , hope this helps and good luck in finding the cause .

PS Is the engine fault code related to the hegos (heated exhaust gas oxygen sensors). toyota refer to oxygen sensora as air flow sensors not to be mistaken with maf or map sensors.

I have never had a flashlube kit fitted to any of my cars as I always understood that you would only need to worry about burning valves out with prolonged high speed motoring. I havent ever had a valve problem.

Mike

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My LPG fitter said a lot of problems some people get with LS400/430 LPG systems is simply down to too small a feed pipe from tank to engine, the fitters save moiney by fitting a 6mm pipe instead of a 8mm.

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hmmmmm ... what are the first symptoms of burning out valves. he fitted a flashlube (?) kit for me.

It's done about 8000 miles since the conversion and seems to be running fine.

Mike

Hi Mike the LS has hardened valve seats the gs 300s don't. Flashlube isn't needed on the LS but a lot of installers fit them as a matter of course.

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hmmmmm ... what are the first symptoms of burning out valves. he fitted a flashlube (?) kit for me.

It's done about 8000 miles since the conversion and seems to be running fine.

Mike

Hi Mike the LS has hardened valve seats the gs 300s don't. Flashlube isn't needed on the LS but a lot of installers fit them as a matter of course.

Cheers for that Mike.

Regards Mike

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Any update, did you get the faults fixed.

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No despite probably 30 hours (extra) of the fitters time, and the involvement of Romano the engine warning light is still on and the LPG consumption is 22 on a run and 17 round town whereas it's 30 and 22 on petrol. Romano just shrugged their shoulders and says some cars are like that.

Mike

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I think that the guys on here who are suggesting that the pressure is too low could be right. Dependant on the vaporiser they fitted, it might not be able to supply enough gas to power the engine properly. Ask if there is a low pressure sensor fitted (there should be one fitted so that the system cuts back to petrol when you run out of gas) and if there is try this - as you come onto the slip road for the motorway slam the throttle to the floor and allow the car to accelerate at maximum until you are above 70. This uses maximum fuel and if the LPG system does not switch the car back to petrol while doing it, then you can eliminate pressure as a potential cause.

With my Cosworth Scorpios I had to have dual vaporisers fitted to be sure that the pressure could be maintained. I only have a single one on my LS430 but I haven't had any issues unless I am almost out of gas and then I get the symptoms I have just described.

HTH

Tc

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