Oxygen Sensor on 6 cyl EF Falcon - Ford Forums - Mustang Forum, Ford Trucks, Ford Focus and Ford Cars

rfoden · 08-03-2002, 06:14

Can anyone help with determining whether the oxygen sensor is OK? The car has a dual fuel system and I have a problem where the car hesitates on petrol when coasting, (it does the same on gas, but loses power intermittantly only on gas which feels like it is out of fuel)
You can correct the problem by releasing the foot off the throttle and then accelerating again. I have a simple 3 LED display - (red for rich, yellow for good, and green for lean) for checking the oxygen sensor, and when the problem occurs, all 3 LED's light up, indicating that the car is running rich, good and lean - all at the same time! When I release the throttle and again accelerate, the system goes back to normal ie. the test LED unit indicates that the car is running rich on acceleration, lean when de-accelerating etc. - ie. either one or 2 lights are on. Any help here is appreciated.

Aussiblue · 08-03-2002, 06:34

Disconnect the wires from the )2 sensor and check that you get battery voltage between the rwo wires (grey/yellow and black/dark green). Then check the two wires on the diconnected O2 sensor for continuity (near zero ohms). Reconnect and run the egnine from cold for about 60 seconds (+ or - 20 seconds). The voltage at the ECU terminla should around .85 volts then pulse between .1 volts and .85 volts. If the voltage remains below 0.5 volts its running too lean if it reamins above 0.5 volts its too rich.

It sounds to me if the 02 sensor is OK but something bad is happening to the fuel injection system at coast. Start by checking for a loose vacuum hose and ensuring the PCV valve is OK. Next check the ISC solenoid and the TPS sensor and that the throttle butterly opens and closes cleanly.

Aussiblue · 08-03-2002, 06:34

PS any fault codes?

rfoden · 08-03-2002, 06:43

Thanks again Blue for your advice.
I will check this out (the only confusing thing here is that the car plays up on both fuels, where LP gas doesn't use the injectors) I meant to also say that the spark plugs and leads have been replaced. I will have to get another repair manual before I check for any fault codes (if any), as mine has disappeared!

Aussiblue · 08-03-2002, 07:06

Ok then it sound like the air supply part of the mix needs investigating; the ISC, TPS and butterfly.