I can't figure it out. My 1993.5 Na has truble from time to time. When driving it will idle down to 100-300 rmp and shake. Sometimes it will stall all together. If I can catch it and turn on the AC the rpm come up and it stops shaking. Again if I turn off the AC sometims it will fall back to the 300 and others it will stick around 1000. any Ideas????? Thanks for the Help.