Porous welds

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So I just do hobby welding and my little Hobart 140 will about 80 percent of the time lay down dirty porous welds and about 20 percent proper welds.   I am welding 18 guage with a 25/75 mix.   So far i have tried a new tank of gas, replaced the regulator and liner, the non flux wire, and made sure the metal was clean.   I have had the tip off more times then i can count and the passeges are free.   The polarity hasnt been reversed and if i put the tip in water it does blow bubbles.  The guage is at about 30 when i squeeze the trigger and the solenoid is working    Its driving me nuts and i have no idea what else is left to check.   Any more ideas would be appreciated.
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Originally Posted by Markbrudjar

So I just do hobby welding and my little Hobart 140 will about 80 percent of the time lay down dirty porous welds and about 20 percent proper welds.   I am welding 18 guage with a 25/75 mix.   So far i have tried a new tank of gas, replaced the regulator and liner, the non flux wire, and made sure the metal was clean.   I have had the tip off more times then i can count and the passeges are free.   The polarity hasnt been reversed and if i put the tip in water it does blow bubbles.  The guage is at about 30 when i squeeze the trigger and the solenoid is working    Its driving me nuts and i have no idea what else is left to check.   Any more ideas would be appreciated.
Reply:What is the size and grade of the wire? Is the base metal plain mild steel? What current setting are you using, and which polarity is the gun?If you disconnect the feed rolls and block the nozzle of the gun and trigger it, do you hear gas escaping towards the rear of the nozzle/gun or near where the wire feeds into it? That is, anywhere that air could be getting pulled into the conduit/gun while welding?Does the cited gauge show pressure or volume? Any pictures of the equipment and of the welds, both bad and good?What happens if you try laying beads on a thicker piece of steel, perhaps 1/8-1/4" thick, first using the present setting, and then using higher ones?