Having some difficulty with the car when running on gas. RR4.6 Thor, Stefanelli SIS system has been fine for 35k now missing on gas. Runs fine on petrol
Live data read of OBD shows O2 sensors working correctly and short term – long term fuel trims as expected. No fault codes
When first switching to gas car misfires heavily. Bank 2 O2 sensor shows rich and STFT moves to minus 25% as stays there. This improved the misfile some. Eventually LTFT also reduces injector times and misfire reduces to a degree where it’s almost gone.
Looking at the injector times I can see that, on petrol both banks are even and on gas bank 2 is shorter, which given the above is what I’d expect.
So, what’s the problem?
As part of a service I’ve fitted new plugs and leads.
Compressions test ok
Swapped the injectors bank to bank, no change in behaviour
Swapped O2 sensors bank to bank, no change in behaviour
Whilst running on gas removed the fuel pump fuse to kill the fuel pressure, no change in behaviour, so it’s not a leaking petrol injector
Even with heavy misfire removing plug leads one at a time or disconnecting gas injectors one at a time does not really show a specific cylinder is the cause of the misfire, it’s a case of all have about the same effect.
On gas with the misfire several fault codes come up, all refer to rich mixture and o2 sensor behaviour, but this is because the mixture is rich and it does send the sensor out of range some times.
So what’s making one bank rich on gas? I’m beginning to think it might be a gas injector wiring issue or even the gas ECU, but then the injector times all show even bank to bank albeit short on bank 2 as a result of fuel trim.
Also, does anyone have a pin-out diagram for the SIS ECU , I want to check the injector wire continuity
Does anyone have the calibration instruction for the Stefanelli SIS system?