Ok, so I got all my plugs replaced and a new coil on cylinder 8. #8 was misfiring every time . Dealer said this may have caused some damage to my Cat and to watch for my engine light indicating possible problems. A week later my engine light comes on. P0420 Cat System Efficiency Below Threshold Bank 1. Would Cylinder 8 effect Bank 1 on a 2006 F150? Any inout appreciated. She is driving sluggish up hills.

 

I guess my question is, is Bank 1 the Drivers Cat? If so, would the bad Coil and Misfire on Cylinder #8 be a possible culprit? The dealer said the gas would have gone straight to the Cat and begun melting it when burning...

 

Bank 1 is passenger side. Go to a muffler shop and have the system tested for excessive backpressure, both sides.

 

No and no.

 

P0420 and P0430 are left and right cats. I've had long tubes with hi-flow cats since the truck was brand new and have always had that issue. I believe it's due to the cats not reaching optimal temps when the sensor thinks it should. JDM sells O2 bungs that extend the O2 sensors out to counteract this BUT it did not work for me so I just had them disable it since we have no emissions checks in CO. if you clear the code it will come back the next day or on a lengthy drive FYI.

 

P0420 is passenger side, P0430 is driver's side.

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