Originally Posted by Jacob.P93
Do you know where to look to find the reason? And I plan on removing them.
As far as the cause is concerned it is usually an unattended misfire or running too rich. If you have very high mileage I suppose they may just eventually fail. The computer may sometimes indicate that there is insufficient exhaust flow but computer will not always point you straight to the problem. I remember you mentioned rough idle but are you havi g rough operation also while driving? Any loss of power?