I have a 1989 3.0L Caravan, after I changed the distributor cap, rotor and spark plugs, plug wires and air filter the van as been pumping black smoke out. When I remove the intake from the air filter box there's a small puddle of gas...ie, its burning rich and hence the black smoke. Does anyone have any ideas on what is causing it?? The van was badly maintained before, and the plugs I took out was very worn. Could it be the O2 sensor????