Truck running rich!

[speed_demon]

I finally got my truck to run smooth but its still running rich. The plugs are powder black color, it struggles at idle and the exhaust leaves a black spot on the ground. If I prevoke a small vacuum leak it runs much better and the exhaust is clean. My ECU coolant temp sensor seems to check out but I haven't been able to check anything else. All the plugs are the same and it doesn't miss so I don't think its a leaky injector. I pulled the vacuum line on the fuel pressure regulator and it doesn't leak although the fuel pressure regulator still could be running at too high a pressure. I don't have any way to test the fuel pressure. My next thought is the o2, MAP, MAF (I cleaned it already), or intake air temp sensor.

I want to test the o2 sensor but don't know what wires are what. I know two are heat and the other two are signal. Which wires are which?

What are the most likely causes of a rich condition?

btw, when I hooked up a code reader the tests ran (rpms went up and down, ect...) but the result was always "unresponsive".

 

[MAKG]

Run the KOEO test before even admitting the KOER test exists.

Read the instructions for your code reader. You don't hook it up while the engine is running.