You mention Open Loop, and the sensor the computer uses to set Open Loop or Closed loop wasn't mentioned?
The ECT(engine coolant temp) sensor is what the computer uses to decide to run Open Loop or Closed loop.
On the 2.3l it is on driver side near the front below intake, 2 wires.
You need to drain coolant before removing this sensor, or it will make a mess.
There is also an ECT SENDER, it is for the dash board gauge only, 1 wire.
If computer is in Open Loop idle will be high, 1,100+ RPM, if that's not happening on cold start up then replace ECT sensor.
It could be another issue but most likely ECT is telling computer engine is warmer than it is, so idle would be lower and fuel mix would be too lean so engine would stumble until it warmed up.
Part of Open Loop is the Choke Routine, Choke is needed on all cold engines, fuel injection doesn't allow for a Choke Plate so computer needs to run the "choke routine".
If you want to test ECT sensor, one wire will have 5volts from computer, the other wire will have 3volts depending on cold engine temp, when fully warmed up that same wire should be below 1volt, if ECT is showing under 1.5volt cold then computer just thinks you are restarting a warm engine, so wouldn't run full choke routine.
There are codes for ECT sensor problems, but only if it doesn't show it is warming up, or has no voltage at all, so it can fail with just lower voltage than it should have, causing the issue you describe and no Check Engine Light
Last edited by RonD; 01-09-2016 at 12:05 PM.