Lambda Confusion

[Jonny_b]

What’s the best way to test a Lambda Sensor?

Colour Connections I have are:

Black Ref. (out)
Red Ref. (in) and Heater (+)
White Heater (-)

Are these labelled correctly?

Saw description at
http://www.lambdasensor.com/main/mcolours1.htm

Possible Test Method
Connect multi-meter to Black wire and Earth on engine. Watch for fluctuating voltage at idle and slowly open the throttle. 0.2v – 0.8v = correct range

Check heater wire voltage above 12v, connect multi-meter to Red wire(+) and White wire(-)

I prefer to test at the lamda probe (rather than the ECU). Is the best way to press the multi-meter leads through the wire insulation at the lambda? Or should/can I disconnect the lambda plug and connect through there?

Thanks

Jon

[Pupp]

What's actually the running problem that prompts the testing need?

[spend]

Stick the probes from your mm down the connectors to contact the connector pins.

Dave

[blitzracing]

The wiring is correct, if you are using a digital meter it may not read that well as the voltages switch rapidly, and analogue one is better. You may see glitches up to 1.2 volts, but this appears normal.

mark

[Jonny_b]

Thanks confirming the wire connections are correct. I will push the multimeter pins down to the connectors at the lambda. Cheers.

Running problems include:
Engine sometimes has one slight misfire then stalls at idle - which clears once the engine is switched off and left for 5 minutes
Hesitant acceleration and feeling underpowered
Engine seems to stick at 2800 - 3000 rpm in top gear on the motorway – feels flat and engine note changes
Rev counter seems to slowly bounce around too – up and down by 400 rpm when above 1500rpm

I have
Cleaned the stepper motor
Replaced plugs which were very rich (hence checking the lambda)
Replaced leads and extenders
Replaced dizzy cap and arm

I have a 94 chim and do not have an ecu fault code reader plug fitted, so I have to test sensors individually. Looking for an ecu plug off a loom at the scrap yards at the moment.

Slowly running out of ideas, advice appreciated.

Jon

[blitzracing]

If the rev counter is bouncing, its likely to be ignition related,(Low resistance plug leads or sprurious triggering of the low tension side)as the ECU cant do this as it has no control over the ignition.I do wonder as the lambda probes measure unused oxygen in the exhaust and not the actual mixture, what the effect of unburnt mixture would be. In my understanding, the oxygen would be up as it had not been used, so the ECU would think the mixture lean, so try and richen it, but I may be wrong. The fault codes that the ECU produces do seem to be able to pick up misfires however by whatever means, so it may not be that dumb. Each bank controls its own mixture, so if all 8 plugs are rich, its unlikley to be a probe. Symptoms point towards AFM, but Ive run my car without the AFM, and the lambda outputs are still ok even though the exhaust stinks?? It should drop into fall back mode if the AFM falls ouside its parameters, that will make it run richer. AFM output should be about .6 volts no air flow, rising to about 1.7 volts at tickover. (Aprox). The ECU warning light should come on, BUT I dont think the British ECU's have this bit of the programming turned on, even if the light is connected. Just a ploy to stop the DIY' er fixing it!

mark

[GreenV8S]

blitzracing said:

In my understanding, the oxygen would be up as it had not been used, so the ECU would think the mixture lean, so try and richen it

Yes, the ECU can lock itself into a rich misfire if it is running closed loop with too much authority.

[blitzracing]

Found this, some really useful tips on the subject.

http://www.roversnorth.com/web/downloads/rnnews/NS...

Mark