What will cause my car to idle ok when I first start it up, then go crazy shakeing, and blowing black smoke out the exhaust. It runs strong on the road, but just "throws a fit at idle, sometime) I have replaced the map sensor, and thats no help. I don't want to just throw parts at it. Any help???
Rough Idle, Black smoke on 1991 Saturn SC
by evilweevil in Pottsboro, TX on February 24, 2009
ANSWER by Russ on February 25, 2009
The map sensor was not a bad guess - How about the vacuum line to the map sensor. Throughly check the vacuum line for cracks or other damage. If the hose is OK the next step would be to look at engine dada with a scan tool while the problem is occuring to see if any sensors are out of range.