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You have either parasitic air (vacuum leak at idle) which the ecm is trying to correct by adding fuel, or excess fuel from another source ( whether that's oil or petrol you will need to determine)

Graph both O2 sensors (up and down stream), and ltft and stft at idle and 2500 rpms for at least 30 seconds and report back.
That actually sounds like a good theory. And I'm pretty sure it's fuel smoke coming out from the exhaustion.
But why does it only happen when driving for 60km or more? If there's a leak somewhere shouldn't it be doing it all the time?
I'm thinking about doing a compression test to see if there's anything there that can guide me further.
 

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Compression test is advisable, as well as a fuel pressure drop test. If fuel pressure drops greater than fsm spec then a leaking injector is a good possibility

Unfortunately I don't have the pressure over time specs handy, someone will be able to post the chart.

Graphing the fuel trims and O2 sensors will help to determine if its air or fuel.

Leaks can appear as things get hot too, and be non existent cold. I hate chasing them, smoke testing a hot engine is never fun.
 

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Unfortunately still no solution for the problem.
In my case, there is one thing, that I have noticed. I made extra exhaust gas test.
In idle (meas.2 in picture) my HC value goes slowly up.
In revs it cleares out, and starts to rise again after some time in idle.
View attachment 106822
Did you ever try to change the O2 sensor?
I've just changed mine yesterday.
Drove for about an hour today, and this time everything was fine. No white smoke!!
Maybe it's a coincidence. We'll see 😃
 

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Unfortunately still no solution for the problem.
In my case, there is one thing, that I have noticed. I made extra exhaust gas test.
In idle (meas.2 in picture) my HC value goes slowly up.
In revs it cleares out, and starts to rise again after some time in idle.
View attachment 106822
On both tests the Lambda is reporting a rich condition, you need to sort that out, if left too long it will destroy the CAT..
 

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ove for about an hour today, and this time everything was fin
I have changed A/F sensor, but not the O2 sensor after cat..

About trims and sensors:
at idle, after driving engine warm: LTFT is steady about -12%, STFT is near zero (+- 1%).
at revs: LTFT is about minus 3-5%, STFT plus 2-3%
at idle, aboutafter 2 mins idling: LTFT steady -12%, STFT jumps plus 2-5%
Sensor 1: sensor mA jumping 0.01-0.03 (at constant high/idle revs)
Sensor 2: tries to hold 0.74V. Chnges for moment if I change revs, and goes back to this value.


Font Electric blue Multimedia Screenshot Rectangle
Font Operating system Electric blue Rectangle Electronic device
 

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Post the readings for the B1S1 in volts, 1 volt is ideal, a +reading is lean and a -reading is rich..
 
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