Misfire

[robbie1944]

Hi
My 2003 Lexus rx300 lpg which is a BRC system seems to misfire when you put your foot down over 3000revs on normal driving at around 2000 revs it runs very smooth

Any ideas would be very helpful

Bob

[Brian_H]

More info would help, if you can answer any of the following for example?

Does it do the same on petrol?

If you have access to any diagnosics, can you tie it down to one cylinder causing problems or see any other fault codes?

Has it had spark plugs or anything else done prior to this starting?

Is this a new install with this fault, or has it been working and suddenly starting playing up?

[robbie1944]

Thanks for that I will get all the information I can

[robbie1944]

Further to my question

Okay when on petrol

No codes showing

Plugs changed about 20000 miles ago

Took it today and gave it a thrashing very rare for me to do, over 4000 revs it switches back to petrol so guess it could be the vaporiser.

,

[robbie1944]

Also has been fitted for about 10 years

[Brian_H]

It could be a few things - it might help to see what the trims are doing when its starting to struggle if you have access to anything that would show them.

Its a long shot, but it might also be worth checking the gas filter (its rare that they get blocked up enough to even notice, but if its never been changed it would be an idea to at least have a look at it. Equally another thing that is possible and more likely is that the solenoid on the vapouriser is gummed up and restricting flow - this is fairly easy to take apart in most cases and clean up to rule it out (would cause similar symptoms to a tired vapouriser).

Any particular reason for suspecting the vapouriser? If you have access to the BRC software it would be worth checking the temperature its showing for the vapouriser/coolant at the time, just in case its not getting a good supply of coolant for any reason - equally check that the coolant level is where it should be on the car, as the heater circuit tends to be one of the first things to stop getting any coolant when it gets low, and usually this is where the vapouriser picks its supply up from. Any signs like frost on the pipework around the vapouriser or the vapouriser itself could be indicating a coolant flow issue - once the engine has reached operating temp the vapouriser should be hot to the touch if its working correctly.

Given its ok on petrol and not logging any codes would suggest ignition is probabbly ok, though LPG will show up any slight faults which you might not even notice on petrol. Can't comment on the miles you've done on the plugs as don't know the car or the plugs you've fitted to say if they should be due for a swap or not, 20000 would be overdue for some vehicles particularly if on the regular copper plugs, but may still be ok on Iridium etc.

[robbie1944]

Hi Brian

Thanks for that information I did change the filter last year about 6000 miles ago,

Unfortunately I cannot connect a laptop as mine died last year and am only using an iPad

Will have a look at the solenoid as I know the water level is ok as I check it regularly