I have a 94 GS 3.8. Runs fine except on occasion it cuts out when driving, and when I stop. On the occasions when stopped,it will surge as the tach needle goes up and down then it stalls. I can smell that it is running rich, and mileage is only 21 mpg, vs my Monte Carlo with the same 3.8 -27 mpg. I changed the thermostat, pump relay, plugs are ok. Car starts right back up, and will run fine for a while. Does it in winter, and summer. Won't throw a code. Any ideas? I don't want to get into hanging parts.

remove the O2 sensor and check for carbon build-up, if there is it needs replaced

Thanks, I'll try that. Looks like there are two of them. Is it possible to clean them instead of replacing?

no, they will work even worse, they would need replaced if that is the problem.

if they are good the next step is i would check the timing.

It is impossible to check or adjust the timing because this engine (Vin L 3800 V6) has an electronically controlled distributorless ignition system. I would check your Mass Air Flow Sensor to see if the filaments are dirty. I might also suspect a bad Coolant temp sensor.

impossible to adjust? yes. impossible to test? no. if the timing is off it indicates a bad sensor input.