#4 cylinder not firing
 

I got a 94 altima and the left most cylinder is not firing. When I installed a header this particular cylinder was black and gunked up and the others were alot cleaner. Also the other cylinders header pipes changed color from the high temp but the far left one stayed silver. I want to test for spark but I don't think thats the problem if the rest work. Could it be the signal to the injector thats not functioning? Or maybe some coolant got into the cylinder from a bad Intake manifold gasket? Any suggestions?

RE: #4 cylinder not firing
 

does the car feel like its misfireing, cause if it is i would simply just check for spark on that cylinder, also do a compression test to across the board just to make sure also. check your distributor connections and make sure theres no corrosion or bad connections either, but at least check for spark cause if you do that its one less thing that could be the problem. you have to diagnose the problem not guess the problem.