1995 Hyundai Accent

Engine Performance problem
1995 Hyundai Accent 4 cyl Two Wheel Drive Automatic 90000 miles

I replaced the o2 sensor and checked every thing I can think of. The engine starts very good at all temps. At startup it runs very rough at idle for 5 - 10 minutes then smooths out. At any acceleration it hesatates very badly then takes off with quite a miss clearing up quickly. When I let off the throttle it quits or almost quits before idleing rough for a 5 - 10 min period and smooths out again. Any help would be appreciated. Thank You
October 10, 2010.

1995 Hyundai Accent RUNS RICH AT IDLE

Probable causes of an engine running rich are as follows: 1. Excessive fuel pressure can be cause by restricted fuel return line or defective fuel pressure regulator.
2. Defective Oxygen Sensors.
3. Leaking injectors and fuel pressure regulator.
4. Coolant temperature sensor out of calibration.
5. Restricted air intake system

Oct 10, 2010.
You mentioned coolant sensor calibration. I have never heard of this. Could you please explain and also which coolant sensor.
I do not think this is the problem as this happens at all temps.
Thank you again

Oct 12, 2010.
The CTS tells the computer to enrich the A/F mixture during initial cold starts before the oxygen sensor takes over the control of fuel at closed loop if its out of range it'll be telling the computer to give fuel when not needed all the times

Oct 12, 2010.