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      07-10-2018, 01:21 AM   #1
tmarino
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INPA Rough Running Screenshot

I just completed some service work on my 2007 E90 328 with coils , plugs and a faulty VANOS solenoid that showed up on my first scan a week ago. Everything went well, the car started up and I cleared the error code. Car runs well but has a slightly rough idle. I payed through some of the INPA screens to see if I could spot something out of the ordinary even though I donít completely understand all of it yet.
I have attached the filtered rough running screenshot and cylinders 1-5 look identical but 6 shows a big difference. Not sure what it is but itís something!
Can anyone help me out in diagnosing this idle issue? I have screenshots of some of the other pages if anyone needs more info.
Any help is appreciated as Iím trying to learn to use this software correctly.
Thanks Guys,

Tom in Reno
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      07-19-2018, 09:15 AM   #2
SG_E90
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Thoughts on trying a new fuel injector depending on your mileage?
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      07-21-2018, 01:13 PM   #3
tmarino
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Car was idling perfectly before I put new coils, plugs, etc. Using that old saying...'the cause of every problem is a change'.., I'm leaning towards just buying one new coil and plug and replacing cylinder 6. Can't hurt a thing and gives me spare just in case.
Thanks for the input.
Tom in Reno
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      07-21-2018, 06:01 PM   #4
gbalthrop
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Quote:
Originally Posted by tmarino View Post
Car was idling perfectly before I put new coils, plugs, etc. Using that old saying...'the cause of every problem is a change'.., I'm leaning towards just buying one new coil and plug and replacing cylinder 6.
Your cylinder #6 MAY actually be developing MORE power than the other 5, or at least as compared to cylinders BEFORE and AFTER in the firing order: 1 - 5 - 3 - 6 - 2 - 4.

Question is: What does higher positive value for cylinder #6 as compared to others mean? Does that mean MORE power developed by that cylinder as compared to those before & after in firing order (cyl 3 & 2) or less?

I haven't been able to find anything reliable as an explanation of Laufunruhe/ Rough Running. Closest thing I can find is Bentley's explanation of "misfire" as a condition where the crankshaft speed slows slightly as measured by the Crankshaft Sensor on the power stroke of a certain cylinder. The following is found at page OBD-4:
Misfire detection. This strategy monitors crankshaft speed
fluctuations and determines if an engine misfire occurs by
monitoring variations in speed between each crankshaft sensor
trigger point. This strategy is so finely tuned that it can determine the
severity of the misfire.
It would seem to make sense to me that the higher a Positive "Laufunruhe" number for a particular cylinder, the more power developed, while the more Negative the number, the less power. THAT is ONLY a SWAG on my part. It IS supported by the fact that when I replaced ONE coil with an identical new coil the Laufunruhe for that cylinder was several hundredths Higher than the others for several weeks after which things got more equal. NO perceptible roughness (or misfire code) at any time.

Any theories or actual knowledge on what the readings mean?

George
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