Engine Performance problem
1989 Chevy Silverado V8 Four Wheel Drive Automatic 292000 miles
" I have an '89 Chevy 4X4 1500 w/350 and auto trans. It used to get good mileage, 17-19mpg and now it is doing very poorly 1/8 of a tank to 30-35 miles. I have replace the complete fuel system from the TBI to and too include the tank. I have checked all the sensors and they seem to be in spec. I have installed new injectors and regulator in the TBI. But hot or cold, it stills smells rich coming from the exhaust. I really could use some help here. &Quot; All fuel lines and the fuel pump have been replaced. Checked for intake manifold vacuum leaks a TBI and heads. No change in idle.
Since you've check the CTS/O2 sensors and it checked out -try checking the fuel pressure if its within specs, also inspect the fuel return line for blockage
December, 8, 2009 AT 10:37 PM
When mine was new 1991 or so, the dealer replaced the coolant tempo sensor on the thermostat housing.
It can causes the ECM to think the coolant is 100% cold or 100% hot in the range of the sensor. If the ECM thinks the coolant is cold, it will run in warm-up mode which is really rich. It was also having a hard time starting.
Also, you said you checked the sensors. How about the sensor plugs and wires?