Re: Lambda Sensor Test? Longish

Hello,

> > Is it possible to test a Lambda Sensor of a Escort/1.4i/1994?

Yes. You can do this either on the vehicle or off. I do them on.

You need a high impedence ohm meter- virtually any digital reading DVM is high impedence these days, and a blow lamp.

If your doing it on the car you will need to hook up to a good earth (neg term on battery) and the white cable from the o2 sensor- usually at the multiplug connector. You may want to add in a temporary lead to a point where you can easily connect to when the engine is hot and running. Whilst your here, check the heater is working- 12v on the black wires.

Find a point in the induction system where you can induce an air leak post throttle- part of the PCV system is usually easiest.

Drive the car under load to full working temperature, connect up your dvm and allow it to idle. With a working o2 sensor and the ecu in closed loop control you should see the voltage swinging back and forth at least once per second from ~0.2v to 0.8v. Ideally twice per second, but a slow reading dvm may not show this. By creating the air leak you should see the reading go high (high oxygen) which the ecu interprets as 'go rich'. Introducing gas from the *unlit* blowlamp the reading should drop (low oxygen) and the ecu should then counter with less fuel. The ecu only has about 10% trim capability from the o2 sensor, so creating a good leak or adding plenty of gas should see the reading stay high or low.

Testing off the car, again with dvm hooked up and 12v applied to the heater (if fitted) heat the tip of the o2 sensor til you get a reading on the dvm. With the flame away from the tip you should see a high reading, and vice versa. This will only prove if the o2 sensor is capable of switching.

If when on the car a known good o2 sensor isnt switching and tends to be stuck in the go lean state, then the ecu isnt entering closed loop operation, which could be caused by a plethora of faults.

Hope this helps. Tim..

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Tim..
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Tim I can only assume you copied this from somewhere cos I'm afraid it isn't up to your normal excellent std.

On a Ford 1.4 the 2 white wires are the heater and the black one is the signal. If you induce an air leak the voltage will drop.

Graham

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Graham

Graham, you are indeed correct, think i had consumed far too much moonshine earlier on. Normal service hopefully resumed!!!! My apologies for any confusion caused..

Tim..

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Tim..

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