Puzzled by emissions.

Replied by talkingcars on topic Puzzled by emisions.

Posted 6 years 4 weeks ago #188301
Plugged in the new ECU, cleared old fault codes, matched it to the 5AS, started the car, exactly the same readings on live data and exactly the same faults coming up......


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Replied by cairnsys on topic Puzzled by emisions.

Posted 6 years 4 weeks ago #188311
I was wondering if perhaps the pscan couldn’t detect fluctuations in the o2 sensor because they were happening to fast so I plugged mine in earlier.

My o2 sensor readings were varying between 0.2v and 0.7v. I’m not sure if those are the correct sort of levels but at least it shows that pscan appears to be able to read variations.

Anybody know what the readings should vary between because I have an exhaust leak (flexi pipe) at the moment?

Robin ;)

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Replied by sworkscooper on topic Puzzled by emisions.

Posted 6 years 4 weeks ago #188316
I'll be checking my TF later today with Pscan so I'll get back later .
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Replied by talkingcars on topic Puzzled by emisions.

Posted 6 years 4 weeks ago #188318

cairnsys wrote: Anybody know what the readings should vary between......


0.8 and 0.2V.


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Replied by sworkscooper on topic Puzzled by emisions.

Posted 6 years 4 weeks ago #188320
Well my TF when warm is reading . Bank 1 0.09 to 0.77
Bank 2 0.09 to 0.88

I can check what it is when cold (not that it would help ) later .

John

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Replied by cairnsys on topic Puzzled by emisions.

Posted 6 years 4 weeks ago #188322

talkingcars wrote:

cairnsys wrote: Anybody know what the readings should vary between......


0.8 and 0.2V.


Sounds like I’m ok then👍

Robin ;)

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Replied by Schrokke on topic Puzzled by emissions.

Posted 6 years 4 weeks ago #188346
When an engine is a longer time of duty can dat cause sticky injectors.
Have you tried a injector cleaner?

If there is no suitable signal from the O2 sensor the ECU put an standard signal in place.
You will see in that case a steady 0.50V on live data. So there is also something wrong with the O2 sensor.
And how is the fuel trim?

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Replied by talkingcars on topic Puzzled by emissions.

Posted 6 years 3 weeks ago #188348
I think there is a wiring problem before the ECU as both the original ECU and the replacement had the same fault of "Fuel pump relay or purge valve or MIL lamp or comms circuit" - my problem is finding that fault.

I had concluded that the ECU uses the default value of .5v when it doesn't get a proper signal from the Lambda probe.

I suspect the wiring problem is before the ECU relay pack as it has relays related to the fuel pump, purge valve and the lambda probe heater circuit.


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Replied by G0RSQ on topic Puzzled by emissions.

Posted 6 years 3 weeks ago #188349
Can you not initially read the signal from the lambda sensor?

You will need an oscilloscope though!

Might be possible to pick up the step changes with an analogue voltmeter though.

You will at least be able to check the supply volts to the lambda sensor and heater, and possibly if it is responding correctly.
by G0RSQ

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Replied by talkingcars on topic Puzzled by emissions.

Posted 6 years 3 weeks ago #188353
pscan says the probe is at a constant 0.49v but inactive and that the heater is on.


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Last Edit:6 years 3 weeks ago by talkingcars
Last edit: 6 years 3 weeks ago by talkingcars.

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Replied by G0RSQ on topic Puzzled by emissions.

Posted 6 years 3 weeks ago #188354
But exactly what is Pscan reading?

Is it reading what the ECU is telling it, or is it actually reading the Lambda sensor status.

You mentioned, and I am sure I have read elswhere, that iif the lambda sensor does not give a sensible reading, then the ECU takes a "default" value as a "limp mode" to keep engine running.

Is PScan displaying this default value?

What does Pscan display if you remove the sensor?

Seems odd the lambda is a constant voltage. Are you cerain it is not faulty?

Anyway this is outside my experience so cant really be of much help!
by G0RSQ

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Replied by talkingcars on topic Puzzled by emissions.

Posted 6 years 3 weeks ago #188360
Pscan is reading what the ECU tells it, this is the value the ECU is using.

The old sensor was also showed a constant voltage, I have unplugged the lead and it makes no difference.


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