Buick Reatta 1991

Would verify if not done so already that your 02 sensors are putting out the correct readings. Perhaps the dealership may already looked at that? You may have one or more injectors stuck open. Sometimes a simple ohm test and comparison can give you an idea there. Other thoughts are if the vehicle coolant system was modified or deleted such as the thermostat it could cause or be part of the issue as well. If the car has been running rich for a long period of time and there is heavy build up in your exhaust the catalytic converter may have already been compromised (plugged up) Good Luck!

hi Brian I have done everything I've got the professional mechanic did exactly everything I did removed everything I put along putting you on hold back on catalytic converters been checked fuel pump vinchecked new computer still stumped all the injectors ohm out properly all the same equalized the strangest thing I've ever seen a simplified engine so simple having problems like this this is worse than a nightmare than a foreign engine

It seemed to do this when it goes from closed to open circuit