1999 S80 2.9 fouling plugs 1, 2, 3
 

Hi guys,

I have a 1999 S80 non-turbo 6 cylinder which is fouling plugs on bank 1, idling rough as guts and lost most of its power.

I have used VIDA to retrieve codes:

ECM-3502 MISFIRING
ECM-3512 MISFIRE CYLINDER 1
ECM-3522 MISFIRE CYLINDER 2
ECM-3532 MISFIRE CYLINDER 3
ECM-261A LONG-TERM FUEL TRIM, BANK 1 UPPER LIMIT
ECM-262A LONG-TERM FUEL TRIM, BANK 1 UPPER LIMIT

I have replaced the plugs and reset the adaptive values/codes with VIDA only to have them come back immediately.

I plotted values I thought would be of interest and attached the graph. Note the fuel trim increasing rapidly.

My first thought was front O2 sensor fault - however they seem to respond similarly and only affects one bank. As the fault only affects one bank I expect that the issue does not lie anywhere on the intake side. It surely must be fuel control systems.

Anyway, I'll stop speculating and hand this off to the experts around here. Thanks!


EDIT - When replacing the plugs I also moved coils from bank 2 to bank 1. Fault remains on bank 1.