G4X N300 random spark when key on

[KennyJ]

Hi,
issue 1:
-i got a RB25det with a N300x plugin ecu.
sometimes when i do a key on it just fires one coil. i was working on the engine last week , had the intake pipe off. turned the key on , heard a pop and saw my turbo spinning. Havent been able to recreate when i want to but it sometimes does.
issue 2:
-some months ago when i was setting it up i turned the coils a few times on and of eacht time with a ctrlS - keyoff-keyon and then i even heard pops in the intake , i havent tried it cause i dont want to pop a gasket out but that one is definitly recreatable

[KennyJ]

The random fire happened again yesterday

turned the key on , heard a pop under the bonnet , went to start the engine , ran on 5 cilinder for few seconds then went back to 6 in a few seconds

i assume fired with exhaust valve open causing a lifter to extend ? its was low on compression on a cilinder when cranking too

[Adamw]

This will likely be due to a hardware problem.  The ignition drive circuit in early G4X revisions could give a barely high pulse during processor boot-up which was enough to trigger a spark with some ignition systems.  The ignition drive circuit was later revised to fix this.  If you contact [email protected] and tell them you suffer from a "key-on backfire" they will arrange for it to be updated.  I think most of our international offices can do the fix so it doesnt need to come all the way be to NZ in most cases.