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(Post Link) post #1 of 6 Old 17-12-09 Thread Starter
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Regarding a great deal of posts on the subject of fuel economy I decided to check my twin spark and give it a good going over, as I like interrogating vehicle control systems I went through all of my engine sensors for correct operation.

Looking at the live data from the lambda sensor (o2 sensor) it pulsed from 0.2volts to 0.8volts, this is what would be checked in a garage normally so it's ok you say, hmmm.

I connected up an oscilloscope to then check the time it takes to pulse from lower voltage to higher voltage, there was a problem, it took a good two and a half seconds to complete a cycle, even worse was the curve when holding the accelerator at 2500 rpm.

Strange thing is the car runs lovely, bad thing is this would cause overfueling , possible cat damage and more cash to run the thing.

If you have a fuelling issue don't disregard the o2 sensor as even though a garage may test it as being ok, it's not always the case.
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nice one jake....
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one of the first things I did on Charlotte was change the lambda, although this was mostly due to very strange goings on with the rev counter at first and lack of power.
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Does my 98 phase one have one o these sensors and if it does where is it? Cause mine iddles very irraticly and feels underpowered
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GTV V6 3.0

Out of interest how were you testing this? Were you monitoring the voltage at idle then revving to 2.5K and seeing how long it took to react?

Last edited by benje; 18-12-09 at 22:42.
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(Post Link) post #6 of 6 Old 18-12-09 Thread Starter
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Yes a 98 phase one has one pre car lambda, it could be this that is causing your problem but also check maf sensor too.

I measured the waveform at idle then checked it on acceleration and at 2500 rpm while driving
It was not just the reaction time, when idling the voltage should cycle from around 0.2 volts to 0.8 volts in around 1 second, mine took 3, that's just an example of a slow lambda sensor.
You may be able to check yourself but you will need a fast multimeter, not a cheap one.
Oscilloscopes are not the average diy tool.

If you do have a good meter set to dc volts , connect live lead to black lambda wire, negative to grey lambda wire or a good earth, you should then see it cycle.
While your there check the lambda heater by setting meter to ohms and connecting probes to either white wire from lambda, you should be seeing a resistance of 6-14 ohms when cool.

You will find lambda connector on the bulkhead behind black plastic cover, held on by a single phillips screw or phase two models , it is mounted on the top of the inlet manifold, I don't know about v6's...

Last edited by jakemate; 18-12-09 at 23:01.
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