Ok, I'm going out on a limb here. Have you checked for plugged injectors yet. This is my logic. Since we only have six cylinders, if one or two injectors get plugged or stop working will result in a higher gas pressure in the remaining system. Therefore putting more gas into the working cylinders, hence black smoke and also the fact that the engine will not idle when the CO screw is leaned out and will not idle under 4000 RPM. ----- Original Message ----- From: "Jim Strickland" <ihaveanaccount@xxxx> To: <dmcnews@xxxxxxxxxxxxxxx> Sent: Wednesday, March 28, 2001 1:15 PM Subject: [DML] fuel pressure problems > (formerly subject: frequency valve again) > > When I fixed the wires to the fuel pressure regulator and hooked the vaccuum > hoses back up, the engine ran richer. I've been turning and turning the CO > screw closed, but when it reaches a point where it's not spewing black smoke > anymore, the car will not idle or run at all below 4000RPM.