Slow it down
You've almost certainly heard this before but I really can't stress it enough. Slow down your playing and practice at a speed where you can really concentrate on the technique and synchronisation of your hands. Once you are comfortable with the discipline you can try to speed things up, confident in the knowledge that you can execute all the right movements already.
It's far better to do things in this order rather than jump straight in and try to play at light speed. It will inevitably sound muddy and you'll never work out where you're going wrong anyway unless you take things a little slower.
When playing arpeggios the goal is to make each note defined, in order to achieve this you will need to pick out strings individually. Simply strumming will ruin your timing and sound sloppy.
Practice finger rolling
Rolling is vital to some arpeggio shapes and unless you have a flawless finger rolling technique it could be holding you back. Practice the motion of the roll (not even necessarily while actually playing) until it feels as natural as taking a breath of fresh air. This will go a long way to clearing up those muddy notes!
Pull off perfection
Perfecting your pull off is also really important when it comes to playing arpeggios. Try to make them sound crisp and just as loud as your picked notes. Practice your pull offs in isolation until you get them sounding just right, it can make a huge difference to your sweep picking prowess.
Pay close attention to your muting technique and listen carefully to see how effective it actually is. You may want to record yourself to help with this or ask a friend for their honest feedback. If your muting isn't spot on your sweep picking will never sound right. Try playing slower and you may find it helps you to identify where there is room for improvement.