Welding Tips and Tricks

I'm new to aluminum and I'm trying to teach myself how to weld it, but I'm running into an issue. Things will be going well and then the puddle will randomly kind of sputter or spit back and I'm trying to figure out the cause of this. I suspect it may be from contamination... Maybe the aluminum isn't clean enough? I have a Miller Synchrowave 210 and I'm welding 1/8" thick aluminum sheet metal clippings arranged as lap joints using 90 amps with 1/8" 5356 filler rod, 3/32nd 2 percent lanthanated tungsten, and about 20 cfh argon. Any advice is greatly appreciated.

Check for gas flow obstructions, then crank up the amperage to what it needs to be to weld 1/8" thick aluminum. Your current amperage setting is good for 1/16" aluminum. Bump it up to 170A and mash the pedal to get a puddle going in 3sec or less. Oh, and drop the filler rod one size, or even two.

Take a look at the back side of the piece your welding on and see if your starting to melt all the way through about were it sputters at you.

So what's the verdict??