Smooth running values?

[garrett.fell]

Anyone here have any practical experience interpreting and taking action based on feedback from running the "smooth running values test" available in DIS? I've done a little searching on the interwebs and have not come up with too much - other than it exists.

Here's the backstory....

Ever so often when sitting in traffic I'll notice that the engine is shaking just so slightly. This isn't anything my wife would notice - but I notice it. It's not a constant problem. I just notice it time to time. I decided to run the smooth running values test and see what it told me. I first did this back in January.

Well - cylinder #4 is showing values that aren't very consistent with the other ones. I can't seem to be able to tell what appropriate values are - other than in theory if they are all "0" then the engine is running perfectly smoothly

After my first measurement back in January I ran a bottle of redline fuel system cleaner through the engine hoping that maybe it was a dirty injector causing the problem. I took another reading last weekend and do see my new "values" closer to 0 on all cylinders than they were before so maybe the fuel system cleaner helped a little - but without more data it's really hard to tell

I replaced all of the spark plugs less than 2000 miles ago. I assume the coils and injectors are original. The car has 111k miles. No smoke whatsoever

I guess the next step would be to start swapping coils and injectors around? What's a permissible reading for a smooth running value? #4 looks a bit off The engine passed the intermediate-lever test I administered last summer. Recently I have had a rough-start or two with DIS telling me it was a misfire event across a wide number of cylinders. This was at about 45 F - which is kind of odd because I didn't have any problems with it the few times I took it out this winter in the teens and single-digits.

Here's a graph of my data. It's an iPhone picture of my computer screen taken on a commuter-train. Lol. You'll notice that #4 sticks out a bit and all my running values in the April test are all closer to 0




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[Deansbimmer]

I too am interested in learning more on this subject. I think in theory you are able to determine by looking at the cylinder running conditions and the O2 values to determine if it's a fuel or spark issue.

At least that's what I did to help narrow down my misfire to a failing coil.

Also regarding injectors... I had an M3 once that we couldn't track a misfire on until I sent the injectors out to be cleaned and flow tested. One of the injectors came back with a flow sheet that indicated 30% of the flow of the others, which cleared up after their cleaning process. That fixed the misfire.

[garrett.fell]

Okay. That makes some sense! Lean spikes may suggest the injector isn't working quite right and rich-spikes could suggest an ignition issue....

Oh - I've been semi-following your tear-down and build. I've gotta say - you've got some balls my man!!! 👍


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