I have a 2003 Cadillac Deville PO 171 and PO 174. I also can smell Rich Unburnt fuel at the tailpipe

Question

I can smell hey Rich extra at the tailpipes at Idol

Answer 1

P0171 Fuel trim too lean Bank 1

P0174 Fuel trim too lean Bank 2

This is what a lean condition will do, Lean is where the combustion is inadequate to support a full combustion as a result a partial fuel is consumed, this is a lean misfire condition, several area should be checked, a fuel pressure regulator at the vacuum hose connection may be seeping fuel into the intake system,