I am wondering if anyone else is having fuel injection problems? My 98 S-10 ext cab with 4.3 Vortec with 96000 miles is drinking gas (only 12mpg) and has a strong smell of gas from the tail pipe. I am getting info from area mechanics that this is a common problem with the spider like injection system. I have changes plugs, wires, fuel filter, cap, rotor, egr, cleaned throttle body, and cleaned mass air flow sensor. Anybody? Help!!!

I can add two two extra possible causes: 1) faulty coolant temperature sensor/low coolant/air in coolant. When the engine is started from the cold the ECU enriches the fuel mix to keep the engine idling; this explains why engines idle high (1000 -1200rpm) at start up. As the engine warms up the coolant temperature sensor signals this and the ECU shortens the injection cycle to eventually bring the engine down to a steady idle (700-800rpm). How to check? Most often the coolant sensor is quite separate to the temperature sender, so a correct read-out on the dash board does not necessarily indicate correct sensor function. Using a voltmeter the resistance across the electrical terminals on the sensor can be measured. By removing the device from the car and putting the end of the sensor in a pan of hot water it should be possible to see an immediate change in resistance, it does not matter so much that the resistance goes up or down but that there is a disernable resistance change with change in temperature. Generally high resistance equates to cold temperatures and vice versa. If there is no resistance change commensurate with temperature change then the sensor is at fault. If there is simply no resistance measurable (open circuit) then the sensor is at fault. If the sensor is working correctly check the connector, the wiring and the wiring insulation for faults and possible shorting.

2) faulty oxygen sensor on the exhaust manifold. If the oxygen sensor indicates that there is too much oxygen in the exhaust the ECU will enrich the fuel mix to compensate. How to check? An issue with oxygen sensors is that they steadily lose effectiveness with age and they can under perform for quite a while before they trigger an error code on the ECU. Ensure the connection to the oxygen sensor is robust and clean. As the oxygen sensor only works when hot there is the danger of getting burnt by working on it so a safe approach is to find the electrical connection on the wiring harness remote from the oxygen sensor and to make voltage measurements there. Most garages have systems that can record the amplitude and frequency of the voltage peaks being produced by the oxygen sensor. A less sophisticated means to get some impression of the oxygen sensor function is to use a moving coil galvanometer type voltmeter (analogue needle on dial). Setting the voltage range to 1 volt and by attaching the meter leads across the sensor wires it should be possible to see the rhythmic pulsing and the voltage range of the operating sensor output. If no pulses are seen it could be either a break in the wire or a fault with the sensor itself.