not running right after warm-up
 

My wives 94 LHS recently quit running. I traced it to Crankshaft senor. Replaced sensor,car ran fine for a few miles,then started idleing weird. It's at about 900 rpm then jumps up to about 1300then drops to 500 and stubles. Then back up to normal idle then starts all over again.
It does this only after warming up for about 10 minutes. Runs fine till it warms up.No trouble codes except 12 and 34. Anyone have any ideas?