1995 Cadillac Seville STS?

I've a 1995 Cadillac STS with about 134000km. I had some DTCs for the transmission solenoids. I replaced the solenoids as one of them were broken. But there was still another issue. When i start the car, it stumbles, misses and stalls. I also noticed it was burning ALOT of fuel (strong fumes and smoke from tail pipe). I checked for codes and none found. When i put the key to the ON position, the Service Engine Soon lamp flashes erratically. A bit strange since there are no codes. I thought it might be bad grounds for the PCM. I checked all the ground and power wires for the PCM. They all checked good. Intermittently, while the car is running, the battery lamp would illuminate, the temperature would fluctuate. While driving, intermittently, it felt like the car was in neutral (step on gas pedal, and only the RPMs would raise) and the speedo would also intermittently stop working and then it would kick back in. So i've proper power and grounds for the PCM, everything leads back to the PCM. Some input would be appreciated. Thx!