Volvo Repair: 93 940 Regina F/I surgy idle sticks high and cuts-out, fuel pressure regulator, air control valve

Question
Roger,
I'm the 93 940 owner with the Regina F/I. I have a surgy very low idle, smooth but surgy. When I rev it in Park or Neutral the idle will smooth out and get stuck up around 1500 RPM. The idle will drop as soon as a load is put on the engine.
I have been driving the car now, and when it cuts out the RPMs don't drop right to zero. It's like I press on the gas and there is nothing there. It takes a few seconds to register that the car has cut out. Then the lights come on. I'll pull over, let it sit for a minute and it will start right back up- but sometimes I have give it a little gas for it to start.
I took off, cleaned and inspected the idle control valve. It appears that it is only opening half way. Is this normal?
When I unplug the IAC Valve, the idle drops to about 400 RPM , but it stops surging.
I replaced the air temp sensor. No change in symptoms.
I have been reading what I can find on line(I dont have a book) and read that it could be Air Idle Control Valve, Coolant Temp Sensor or Fuel Pressure Regulator
You told me to check my fuel pump because Regina F/I has a single pump and it lives in the tank, but I don't know how to check it.

Is this still what you suspect after this diagnosis update?
Also what manual do you recommend for this car?
Thank you for your help.
Glenn

Answer
Glenn, It may be the coolant temp sensor but to me its that sticky air control valve.  There is nothing to clean.  either it works or it doesnt.  You can try direct power to the valve to see if its working.  I like to use test leads and the vehicles battery.  Best Manual is the Factory regina manual.  There is also that stupid thing over by the firewall.  I forget what its called but it has a vacuum line attached to it. I have seen those go bad. Roger