07 A8 L 4.2L codes: P0087, P0300, P0301, P0302
 

Hi everyone,

New to the forums. I have my 07 Audi A8L 4.2L Quattro running very rough, misfiring, smoke coming out of exhaust, and looks like fuel is running out of the exhaust. I already replaced passenger side HPFP. Also used some Audi fuel treatment liquid, nothing helps. Spark plugs are good and coils are good. I'm getting these codes:

P0300-Random misfire detected
P0302-Cylinder 2 misfire detected
P0301-Cylinder 1 misfire detected
P0300-Multiple cylinders misfire detected
P0987-Fuel rail system pressure: too low

The P0087 code is very suspicious to me, makes me think that this is something to do with fuel system, that's why I started with HPFP replacement. I would greatly appreciate your help guys. Thank you in advance!

Have you replaced your fuel filter?