I was wondering what is the difference between open and closed loop in ecm operation? My car has an idle and hesistation problem until it gets up to about 190 degrees then it runs great.
any ideas?

 

open loop is when you start your car up - none of the sensors (O2) are factored in for fuel delivery, usually runs rich and wastes gas..
Once it hits a certain temp (i believe) the car will go into closed loop which means the computer will take readings from the sensors to adjust and balance the air/fuel ratio.

 

Idle problem... TPI? If so, I'd say clean out the IAC passageway and the IAC valve's pintle tip. THere's probably a ton of carbon in there hindering air flow. (Air goes "around" the throttle blades via the IAC system when your foot's off the gas pedal.)

 

You mention idle and hesitation. Easy way to check for open loop vs. closed. With engine running put in test jumper same way you would test for codes. This is called "field service mode". If the SES lamp flashes rapidly 2 and a half times per sec, you are in open loop. A one flash per second SES tells you that closed loop is achieved. Your problem is probably not related to ECM loop. Any TG will reach closed loop well before 190 deg. You have another problem.