Mig welding porosity

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Hello, I have an older (early 80's) Linde 225 mig welder that has been giving me problems lately with porosity. I can go along fine on a weld and then I will start getting some bad porosity. I don't think anything is wrong with the welder itself and the gas is still runing as best I can tell. Cleaning the nozel doesn't seem to make a difference. The gun itself is quite old; could be what originally came with the welder.  The nozel is loose on the gun, could it be sucking air in through the backside?  Any suggestions would be appreciated.
Reply:Sounds like a restricted flow somewhere, probably start with the flowmeter and check from there. Could be a pinched gas line. Another thing to check is where the inlet of the welding gun plugs in. If you have someone around have them watch the flowmeter when  you are welding to see if you are losing flow on the gauge.Miller xmt304,  Miller S22 p12, Miier Maxstar SD, Miller 252 w 30A, Miller super32p12, Lincoln Ranger 9, Thermal Arc 181I with spoolgun, Hypertherm 10000 ,Smith torches. Esab 161lts miniarc.
Reply:CLEAN METAL!! I am assuming you are running a flap disk every piece you weld. If not, it needs to be super clean. I know every one says, "ahh, you dont need to clean it that well". But, you really need to.
Reply:A handy tool to have is a hand held flowmeter.  You release the wire feed rolls then sit the little plastic flowmeter on the end of the nozzle.  If the flow indicated by the little ball does not match with the flowmeter at the tank then you can be sure you have a leak.   A common leak is where the gun lead pushes into the wire feeder.  Check the o-rings and make sure that the bayonet is pushed all the way in.  If pulled partly out then the gas will not reach the annular groove between the two o-rings.  If you can feel a breeze on your cheek then you will lose shielding.  Turning your gas flow up too high will cause so much turbulence that you will lose shielding.  This usually happens to people who run 35 to 40 Cu. ft. / hr.
Reply:Thanks for the tips, I will mess around with it a little more and check on what has been suggested here.  I do know on the flowmeter it is set for 20cfh.  I will try out another regulator and see if that fixes the problem.  I do clean the metal as a general rule but in the past when I have not it has not lead to porosity like this.  I am aware of the wind and if there is any I will shut the shop doors.  I believe it is something with the machine and so will check over it again.Thanks