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· Registered
1999 320i M52TU
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5 Posts
Discussion Starter · #1 ·
Hello dear community,
Car is E46 1999 320i M52TU engine, i'm from Europe.
Looking for advice regarding the INPA analogue values i get (sorry for the pics quality they were taken with my phone).
Car is running fine, i get no check engine errors, i have recently did the entire intake/admission part: manifold was taken apart and installed new PCV, new DISA, throttle boots, gaskets, o-rings (including the dip stick one), and redid the vanos with the Beysan system.
However i have some strange values in INPA as you may see in the attached images.
2 questions: First question is about the lambda probe banks 1 and 2, before kat-sensor voltages in this picture:

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From my understanding and from what i read online, it should be at around 0.7ish voltages.
INPA shows me values of 0.7ish for about 1-2 seconds, than for the next 1-2 seconds the values drop to 0.1ish or 0.2ish volts, than they get back to 0.7ish, and so on.
So every 2 seconds more or less, the values change from 0.7 to 0.1 or 0.2, and back to 0.7, and than back to 0.1 or 0.2.......is this normal behavior? I read that these sensors rarely go bad, but still...

The second question is about the roughness: here is the pic i get from INPA, engine running at idle speed :

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As you can see, cylinders 3, 6 and 4 have value of 0 (dead zero), while cylinders 1, 5 and 2 are running on different values (probably a bit hot, i don't know).
If i step on the gas and release it, than the cylinders that previously had 0 value are returning different values (not zero), but when engine comes back to idle speed, the cylinders will return to their 0 values. Is it possible that i need to replace the ignition coils? They have never been replaced and i read that they go bad at some point, and the car is more than 20 years old :) The spark plugs have been replaced 3 years ago with NGK spark plugs.
It is strange to me as the car don't seem to run rough, like in only 3 cylinders out of 6, power is there i have no issues, no hiccups.

Looking for your advices and thank you,
 

· Premium Member
2000 E46 323i, 3.0L, 2.8L and 2.0L Z3's
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2,558 Posts
You have done a lot of work on the car. Well done.

I can see nothing wrong with the values in the photos.

The pre-cat O2 voltages will switch from 0.1 to 0.8V at hot idle every few seconds. So, you are describing the normal operation of the sensor.

The rough running values are all below 1, so they are all good. Nothing to worry about here. These values change as the engine adapts to it's operating condition.

You can read more about the engine data values here: How To Read OBD2 Engine Diagnostic Logs
 

· Registered
1999 320i M52TU
Joined
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5 Posts
Discussion Starter · #4 · (Edited)
Thank you very much for the replies, much appreciated ! Will check the links as well to educate myself on this.
LATER EDIT: Wow, thank you so much to both of you for the awesome, in-depth resources provided. After checking the links, can say i definitely have a lot of info to digest and go through :)
 
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