1989 Chevrolet Silverado

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.
November 27, 2009.

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

Nov 27, 2009.
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?

Dec 8, 2009.