Logging Group 14 (Misfire recognition)

B6/7 S4/RS4
#1

A question about the logging of group 14 that I was mulling over.

How does the “Misfire counter (total)” column work? Does it count misfires in a certain time window then reset to 0 after that window passes?

I initially thought each number was a misfire (So tried summing them), but it just seemed too “clean” that the logs would always show around 300 misfires (~300 rows of 1’s) over a ~29 second period.

So then I had a theory that maybe it’s just a moving window. So if you happen to have 2 misfires within the window, the counter would increment to 2, and you’d get a few rows of 2’s before it reset back to zero.

Couldn’t find any solid information by googling

#2

It counts misfires up to a fixed length of time, then resets to zero. I think it counts for about a minute. If you have enough misfires during that time period, you get a code.

Yes your solid stream of 1s is only one misfire…:slight_smile:

#3

Thanks, had a feeling it was too regular to be one misfire per polling.

#4

I haven’t done any logging in awhile, but if I recall, one of those channels only shows the turning on/off of the knock sensors… Ex: 1 = sensor is on and looking for knock; 0 = sensor is off. The actual knock counts were in a different group, and were quite easy to spot… I’m sorry I can’t give you exact channels/groups without poking around with it on the car. But point being, take another look at what groups/channels you’re looking at, as I think you might be looking at the wrong one…

#5

Definitely group 14 I believe. It does have that enabled/disabled flag, but it actually logs as “enabled”/“disabled”.

One other oddity I noted is that it doesn’t always show values. Not that it shows zeros, but I mean fully blank on both the live display and when logging.

I’ve been getting lots of cels for misfires recently during cold starts, during both startup idle and sometimes while driving around. I pulled the coils and plugs and they seem fine, so I swapped them across banks for the coils, and across banks and flipped for the plugs.

I wonder if any of the fueling components could cause this to happen as well? Especially since they seem to happen when cold.

#6

How old is your fuel filter?

#7

I’m assuming pretty old. I’ve never changed it since I got the car and it’s been a little over 25k kms or so.

It’s next on my list, just haven’t had a chance to head over to Owasco to pick one up.

The misfires seem truly random, so it doesn’t feel like a coil/plug issue. Unless they’re all failing equally.

#8

oh snap really? I am sure I told you to change it right when you first got misfires

I’m going to dig that up on what’sapp and then berate you for not listening lol

#9

Haha I swear that was something I mentioned after I moved the coils and plugs around like you guys suggested. Remember I asked whether the filter was on the passenger or driver’s side?

Do you guys have any good fuel system/fuel injector cleaners you’d recommend? I was thinking of running some of that through before changing the filter so all the cleaned up gunk from before the filter goes with it.

#10

I remember but I thought you were asking because you were going to change it

You can also send out your injectors for cleaning/service, to ensure another part of the fuel system is working well.