Usually no problem going too slow. I think the factory spec is 750-850 or so on the 22RE. I run mine down as slow as it'll run smoothly and not bog down with the alternator or power steering. Mine usually is around 800-850. The idle cut RPM seems to be up above 1000, and too fast an idle just wastes gas if the engine idles a lot. You can pick up a low cost tach/meter for not a lot of money:

http://www.harborfreight.com/3-1-2-half-inch-lcd-multimeter-with-tachometer-kit-95670.html

or many timing lights have built in tach readouts. Very handy for timing the engine.

r.c.brown@ieee.org
TruckEditor@tlca.org
Project: 4Crawler
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