Inverted scope trace

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Inverted scope trace

Postby Technician » Sun Apr 15, 2018 7:05 pm

Can someone please advise if I am doing something wrong or if there is a setting to invert ignition scope traces, I believe the trace on the scope is upside down and even at the time of measuring it I could not find a way to invert it!

I was using the pico probe on COP ignition at the time.

I also attempted to scope the front and rear lambda sensors, the engine was at normal operating temperature and the cooling fan operating, lambda 1 was switching as expected but appears to have quite a lot of noise present, this ensuring the leads are kept away from the ignition components etc did not make any improvements.

Lambda 2 is the read trace, I was kind of expecting to see a slight switching action but it appears as a flat line, I thought of bad connections and re-tried but made no difference. Following the pico automotive guide tests I tried to set the scope as per those instructions, however, the scope traces were significantly larger than my laptop screen area and had to adjust the voltage scales significantly to ensure a reasonable size scope trace on screen.

I have also completed a cam and crank correlation, the engine is a good runner the timing is spot on.

Edited to add; Sorry it appears I did not upload the lambda traces, and after trying to upload twice and doing a compression on it, its still too big?
Attachments
Nissan_Almera_2004_Petrol_20180414-0004.psdata
(17.44 MiB) Downloaded 68 times
Nissan_Almera_2004_Petrol_20180414-0003.psdata
(6.43 MiB) Downloaded 71 times
Nissan_Almera_2004_Petrol_20180414-0002.psdata
(5.4 MiB) Downloaded 66 times
Nissan_Almera_2004_Petrol_20180414-0001.psdata
(290.51 KiB) Downloaded 64 times
Last edited by Technician on Mon Apr 16, 2018 1:15 am, edited 2 times in total.
Technician
TwoWaves
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Re: Inverted scope trace

Postby kona » Sun Apr 15, 2018 10:00 pm

Hi,

It seems that you have questions with a compression in one cylinder. :?:

When measuring the lambda, you selected a probe for ignition. :?:

The straight line of the second probe means you have a working catalyst.

good luck :D
kona
OneWave
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Re: Inverted scope trace

Postby Technician » Mon Apr 16, 2018 1:26 am

kona wrote:Hi,

It seems that you have questions with a compression in one cylinder. :?:

When measuring the lambda, you selected a probe for ignition. :?:

The straight line of the second probe means you have a working catalyst.

good luck :D


Thanks, I agree. When I was scoping the lambda 1 there was significant hash present, however I was confused between amplified hash and significant hash, hence at work I was interpreting the data the wrong way round. During cranking of the cold engine there was a sound that indicated a compression leak, which I have not yet established which cylinder(s)?

Viewing the ignition trace I can see just before the ringing of the winding hash, which I think is the misfire.

As the engine warms up the compression leak (sound) disappears. Referring to the scope trace I seem not to be able to upload (lambda) the trace has very strong severe hash present at both the maximum and lower trace curves voltage levels, along with spikes that shoot vertically downwards and upwards.

This engine has a none start problem that only occurs when it has been stood overnight. I put the scanner on it to do a non-start test but after a few seconds cranking the engine went and started, hence no pid data to look back on that shows a fault area. So tests for another day on that one.
Technician
TwoWaves
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Joined: Thu Apr 24, 2014 10:32 pm


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