Head or clogged catalytic?


I recently had a little hesitation while traveling at about 35mph. I figured it had been awhile since I did my plugs and wires, so I did that. A couple days later after stopping at a light and accelerating again, it was really chugging, not accelerating much. I pulled over and right before it seemed like it was going to stall, it revved up and everything was fine again.

I checked the plugs and didn't like the gap they had (3 electrodes, pre gapped) and two of them had a little black char on them, little enough to just wipe off. Well it kept happening so I replaced the plugs completely, again. Kept happening. Took my cap off and inspected the rotor, tiny bit of corrosion on the tabs but I just brushed it off. Everything worked fine for a few days, now it's doing it again.

now I have no clue, clogged catalytic converter? Fuel filter? The whole engine is filthy so if I had a cracked head or something I can't tell, seems pretty greasy everywhere down there. Valve cover gasket I did a year or two ago. I'm just at a loss here. Any help is appreciated!

oh its a 97 xj