I have a 2002 Dodge Grand Caravan and I am having an issue with it running a touch rich and not getting the gas mileage it should. Here we go, in March the van started to start hard and blow black smoke out of the exhaust. After a 120 mile drive back home, one morning it would not start. I pulled to a mechanic who went out and started it without a problem, he said it was flooded out and probably needed to change plugs and wires. I took it home and changed the wires and plugs. Much to my surprise, no change. The van started hard and then ran really rough with no power for a while and was polluting the air with black smoke. The average mileage was around 12 mpg. I went to the next step and changed the coil pack. No change. Finally took it in and the mechanic changed the O2 sensor and the cat converter. The can runs better but still gets around 16 mpg and still blows a small amount of black smoke. Oh yeah, the air filter is clear and there are no trouble codes either. I am thinking it could be a something with the fuel delivery system maybe? Any help would be great.
Did you happen to take a look at those plugs when you took them out? They may have been trying to tell you something. If any of them looked like they had been burning a rich mixture, that could have pointed you to the problem. I think you may have a fuel injector problem. One or more of them may be leaking, causing you poor fuel economy, occasional to frequent flooding, and black smoke. Your cheapest first effort would be to remove them and clean them with carburetor cleaner. Consider replacing the o-rings at this time, or at least make sure not to lose or damage any of them. If that doesn’t help, check the spray pattern and replace the injector(s) with a poor spray pattern or any sign of leakage. If you are unsure of how to do this, I suggest having a professional do it for you. It takes an experienced set of hands and eyes.