Coolant temp sensor should be tested at 20deg C, you should get reading of 2.2- 2.8 kOhms, and 80 deg C 290-370 Ohms.
Deg F= (deg Cx1.8) + 32; Deg C = (deg F - 32) x 0.56 Pull off plug from ECU and test for continuity between term 21 and coolant temp sensor plug (grn/red wire). The color code on your car can be different, the other wire from coolant temp sensor goes to ignition control module term 1. You can test it for continuity too. The resistance should be approx 0 Ohms. Since you will have the ECU plug disconnected, Test overvoltage protection relay. It is located on the passenger side behind battery, it has a 10A fuse on the top. Switch ignition on, engine off. test voltage between term 1 of ECU and ground, it should be battery voltage. With your multimeter connected try to wiggle the OVP, tap it with a screwdriver, if there is a voltage change, you may have an intermittent connection to OVP, or bad OVP. I will refer you to Steve Brotherton's thread Evaluating Electronic Controls. It is located in DIY. The test he performs will help you monitoring the signal coming to Idle Speed Air Valve. See if there is any relation between the miss you have and current draw by Idle Speed Air Valve. Give me your feedback. Also what readings did you get on O2 sensor. Two more questions. What rpms do you have at idle trans in P orN ? What rpm do you have with trans in gear?