anyone know what could cause this, i have a new pump and filter (new being 5 or so months old)
its just one cat thats dinted though,im still stickin to the cats
the coils arent 5 months old (its a used engine we dropped in, the coils look stock, and i grabbed some to replace the bad ones from my other engine and those where motocraft and i dont know how old they are)misfire after going WOT, but fine before hand
5 month old coils and plugs, new pump and filter
Id do the above take out the 02 sensors and see what the pressure is.
Ok so when cats get clogged or even start to get clogged and air backs up through the exhaust system, causing a stacking effect, when the exhaust valve opens, the waiting old exhaust is shoved back into the combustion chamber, putting more air than fuel into the combustion chamber.Yeah, cats should not affect lean. Lean means somehow you're getting too much air and not enough fuel. This could mean a bad/dirty MAF, vacuum leaks, or bad injectors.
I would lean towards a bad/dirty MAF, vaccuum leaks, or possibly a fuel system restriction upstream of the fuel rails. If both banks are lean it isn't a single side issue, so it's unlikely to be a single injector or oxygen sensor.