I had the same thing happen to my 89 Jimmy 4X4.
It was the temperature sensor on the intake manifold.
When I plugged my homemade computer interface in the temp reading was showing -20 degrees and the fuel was pouring in.
I then disconnected the sensor and the car started running better.
Looking at the temp reading by the computer it showed -40.
Ha, open circuit meant that the computer put in a general fuel mix and that made it run better.
So I went to the auto parts store, got a new temp sensor and my problem went away!
Hope this helped!
Sunday, November 16th, 2008 AT 10:40 AM