scars, ive had this problem with mine. guage often spikes a whole lot, enough to worry me. i completely dismantled it, cleaned it, oiled it and put small amounts in the bottle at first just to try and get it bedded in.
works just fine and dandy now
just try a proper good clean, and i mean taking the on/off out, spring, output adjuster etc its worth the hassle.
these air systems must be the most under-rated of the lot, bargain mine was