i have a 91 caprice and i failed my emissions test because i was giving out too much carbon. I was told that the coolant temp. sensor was critical and to check to see if the thermostat was stuck open. If it was running cold it would cause it to run too rich. well i changed the thermostat cause it was stuck open and i changed the sensor just because. if you have any suggestions please let me know, would like more info before i take another shot at the test.
thanks.

Make sure the air filter is clean, you have no vacuum leaks, the injectors are both spraying properly, and the distributor is timed correctly (should be TDC or 0 degrees TDC if I remember correctly).

The CTS is the #1 culprit in a CO failure on one of these TBI cars, however.

i have a 91 caprice and i failed my emissions test because i was giving out too much carbon. I was told that the coolant temp. sensor was critical and to check to see if the thermostat was stuck open. If it was running cold it would cause it to run too rich. well i changed the thermostat cause it was stuck open and i changed the sensor just because. if you have any suggestions please let me know, would like more info before i take another shot at the test.
thanks.
check plugs for excessive fouling if carboned up replace. also pcv replace and if oil is dark and goopy replace after a week of driving it should run better after the carbon in the combustion chamber is blown out................