LT1_King

iTrader: (1)

my car idles pretty rough and when i get on it to about 3500-4000 rpms it starts throwing out black smoke through the exhaust. could this be a lack of fuel maybe it could be running lean? could this be the fule pressure regulator or if i changed the fuel filter could that help? it's a 94Z A4.

slohatch91

black smoke mean too rich. too much fuel pressure. do you have a fuel pres. guage?

Revelation Z28

iTrader: (10)

check your o2 sensors.

Matts94Z28

iTrader: (6)

check o2's first...i had the same issue before i changed mine

seawolf06

iTrader: (8)

and plugs...

LT1_King

iTrader: (1)

the plugs are new. i went with a friend to a Chevrolet House. we hooked up the Guage and at idle it read about 35 PSI. when he would give it gas the pressure would drop to about 20-25 PSI. would this mean the regulator is messed up or could i start by changing the fuel filter maybe it is just clogged.

Boodyrider

iTrader: (2)

Start with fuel filter. 12 bucks at most auto parts stores.

Boodyrider

iTrader: (2)

Idle pressure, don't forget engine vaccuum is subtracted from static pressure. IE. 16 inches vac is about 8 psi, and static pressure is 43 psi, so you'd see around 35 psi at idle if you didn't disconnect the vac reference from the fpr.

No, you DONT need a new fpr, it sounds like it's doing exactly what it is supposed to.