My number 6 spark plug was black. It looks like the number 6 cylinder is running rich. I havent burned any oil and all my other plugs look like they are suppose to. What could be causing this?

 

Badly leaking injector?

 

I just replaced the injectors so i hope it isnt that how can i check to see if thats the issue?

 

Dry sooty black, or wet oily black?

Watching how your fuel pressure drops might be a clue.

 

Never hurts to get a compression test on all cylinders and see where #6 reads in comparison to the others. The compression spec for the 4.0 is 120-150 with no more than a 30 psi variation between cylinders.

 

Bad plug or wire? Does it miss at all?

 

It doesnt miss at all but does idle up and down all the time

 

Get a fuel pressure gauge on it. Record the readings both with and without the vac hose connected to the fuel pressure regulator. Then, shut the engine off and observe the gauge.

 

More of a dry kinda gritty stuff

 

Those would be carbon deposits. Symptoms leading to either a rich fuel mixture or weak ignition system. If only in one cylinder, check plug wires for resistance, could be a faulty/defective spark plug or check the terminal inside the distributer cap. If those check out good then check your injector for malfunctions.
Plug reading has become a lost art nowadays but you may learn a lot about the condition of the motor by looking at them.

 

Here:

 

Thank you. Most should save this for future reference. Sadly, they nolonger teach this in tech schools.

 

Very tru most people dont know what they are looking at when the look at their plugs and mucj less gap them correctly. I only know what a plug should look like but have no idea what causes the different plug conditions

 

Just read your signature thats awesome and so true about the gun buy backs

 

True stuff, eh?