Hello All,

I have a 1985 VW with the CIS fuel injection system. The car violently stumbles when I give it too much throttle in first or second gear. So far I replaced the spark plugs, spark plug wires, distributor cap, rotor, air cleaner, and thermostat. I checked the timing and tried to adjust the fuel mixture on the fuel injection distributor. Nothing worked. I did notice the fuel pump makes a buzzing noise and it seams worse when I am low on fuel, but it is hard to tell for sure. Its the main fuel pump that is buzzing and I have been told the one that buzzes is not the problem. Its usually the quiet pump that needs replacement. My guess is that it is starving for fuel for some reason. My thinking is that one of the fuel pumps are bad or the fuel pressure control is bad. There is a oxygen sensor on the system and I am monitoring it from inside the car. When I give it throttle, the voltage goes to zero on the meter. That tells me it is starving for gas or the oxygen sensor is bad. I don't think this system has much of a computer system in it. Its mostly controlled by fuel pressure. Oh yeah, I could not find any vacuum leak. Anybody have any other suggestions? The car has about 220,000 miles on it. thanks