Check the batteries 1st and foremost. This sounds too simple, but a lot of people overlook them. Sounds like you're either running lots of batteries &/or AC adaptors. Most of the time the batteries have been sitting on ths shelf too long before you even buy them. Low bats can produce unsuspecting results (like noise, signal loss, spikes). I always go with Duracells myself. Buy a good battery tester. I try to change all batteries out at the same time and always change them before a gig. (Keep the older ones for the TV remote, lol).
A/C adaptors have always seemed to me to produce more noise than batteries. I had all my pedals hard wired for A/C in the 80's until they all got "lost". But that's another story. They were the cleanest sounding pedals I ever had.
Oh yeah, don't forget that the batteries are being drained as long as there's a cord in the input (or output, I can't remember right now), whether the pedal's on or off. So I always pull all the chords out when not using the gear, just to be safe.
Here's a good reference site: http://www.geofex.com/fxdebug/fxdebug.htm
That's the Guitar Effects Debugging Page. Very helpful stuff there, although not updated since 2000.