missfire

[robbie1944]

Hi i have a 2003 lexus rx300 fitted with a brc lpg kit

problem I am now having is when running on a light throttle lpg runs perfectly that is when running under 2000 revs but when you put your foot down as recently been traveling up and down quite a steep hill Sutton Bank in North Yorkshire the car changes down to 2nd or 3rd and revs around 3500rpm it starts to misfire but when I have changed back to petrol runs fine so guess the problem must be lpg any ideas would be very grateful

[Gilbertd]

LPG needs a better spark than petrol so any weakness in the ignition system will show itself on LPG before it shows itself on petrol. When were the sparkplugs last changed? Bear in mind that plugs don't last as long running on LPG either so even if the mileage doesn't suggest they need changing yet, they still might.

[robbie1944]

that is interesting because it is over 15000 miles and not sure when the rear where changed as it is a major undertaking
so I think i will look at that first thanks for the info

[LPGC]

I totally agree with Gilbert about plugs, if the vehicle ran well on LPG before in your ownership it could easily be that it needs plugs changing.

But I know what a pita it is to change plugs on RX300's, so instead of diving in and changing plugs I could understand if you want the LPG system diagnosing.

Plugs top of the list of things to check but it's usually easier to check plugs than check the LPG system, in this case it could be easier to check the LPG system than to check plugs.

Do you know if the misfire generally occurs on the same engine cylinder(s) or is the misfire on random cylinders? An OBD code reader would help determine this and the info could help point to the root problem.

[robbie1944]

it is a total nightmare on this car to check or change the rear plugs that's why I thought of looking at the lpg first and no I put an obd tester on yet but
I think will try that when I eventuall go home as at the moment stuck in North Yorkshire and cant go home

[Rob1944]

Changed all the plugs and coil plugs as it is a nightmare changing the rear ones
The car now runs perfectly
Thanks for advice