I think Simon missed this bit of your reply - The petrol ecu is still active when used on lpg, and will still adjust its trims according to the lambda sensors. So if your lpg side is set too rich it will lean it back off - causing it to be corrected. Doesn't sound like a problem until you switch back to petrol and see it takes a while to relearn the trims for petrol (if they are very far off it may not relearn on some cars until the trims are reset). effectively if the lpg isn't setup with the correct calibration the petrol ecu will be trying to correct it, and the lpg will then be adjusting it as well.4eyes wrote:Thanks Simon. I have read on some American Subaru forums that my engine is tuned a little lean in places, Alot of people seem to have this issue with no fix apparent. Would you be able to expand on the point above about the possible rich set up of the lpg ecu effecting the petrol ecu? Thanks.LPGC wrote:
Has it been mentioned yet that a lean mixture on petrol can cause knock... Lean mixture on petrol could be due to LPG system calibrated too rich.
The real question is does it keep doing it after a few miles on petrol, or does it gradually disappear?