My MIG has been acting up for almost a year. I have replaced damn near everything trying to fix it. It would intermittantly act like a badly worn contact tip. Popping, sputtering, burning back, it was really pissin me off. Well, I finally found the culprit last night.
While I was welding on a roll cage, I leaned against the ground clamp and burned the crap outta myself. There was high resistance where the ground cable bolts to the clamp. I thought I would post this so others won't overlook this basic problem.