David, I would refer to the thread that jay3000 links to above, it details my symptoms and what I did, with comments from others. Best it seems would be to adjust the trimpot with an ohmeter, then re-attach carefully aligned to the scribe mark. Car should run fine.
Fine tune using a voltmeter from pin 2 to ground, connector attached and car idling, by rotating the body of the pot to get that reading (0.7V). This would have to be done slowly and incrementally, tapping, letting the speed stabilize, check voltage.
'91 MB 190E 2.3
'08 RAV4 Ltd 3.5
'83 Lazy Daze m'home 5.7