Race weekend and the car developed an intermittant missfire. Only happened briefly twice. It was like a plug had loaded up. I want to check a few things, change the plugs, etc. One thing that is definately wrong is the o2 sensor is fouled; it goes offline after a few minutes of track use (Innovate E8 code). The car has already been dynotuned. Can I just unplug it from the ms3 unit now as part of my trouble shooting? Other culprits might be: 1) I'm using a one heat range lower spark plug gapped at .028. 2)The tuner didn't like my mini alternator. He said that he measured voltages in the 11.5-12.5 range when on the dyno.

 

It doesn't need one to operate. There a are a few settings that allow a closed loop operation with a wideband. I'm not sure the ECU would respond if these were on and no wideband connected.

 

You should not need an O2 sensor to run the engine (wideband or otherwise). In the absence of one it will just run in "open-loop" (i.e. not actually a loop). The "closed-loop" is usually only used in a specific RPM and load range, around cruise, to fine-tune the amount of fuel. Heavy load and/or high RPM, most cars will be tuned to run open loop. Unless it is badly tuned, it will run fine in open loop without an O2 sensor.

If the Innovate controller (MTX-L, I guess) says E8 after a few minutes of track use, it's probably overheating (too much of too hot exhaust). Sensor may or may not be toast.

 

Thanks. I changed the plugs. They all looked good. Cop connectors look good. Batt is fully charged and alt adds 3 v on startup. I'll just leave the wideband connection alone as you are saying that the O2 sensor isn't used at wot. Race is in an hour! Lot's of great cars, vipers, gt3's, Ferrari's... AR Racing is also there in his M3 ... I'll have the best seat in the house!!

 

It happened again during the race and I had the pull in after 9 laps. Just a random misfire. Not just while under load, but also at light throttle... it went away after a brief cool down and restart in the hot pits. Even if I retired after 9 laps, i still had a great seat for the show.

 

you're running COPs and 0.028" gap?

 

Yes, these COP's are the OEM version on a 2004 msm. There are 2 coilpacks; each on serving 2 plugs. Opinions in the paddock were that one of the coil-packs overheated. Another opinion was that using a 1 heat-range colder plug wasn't cold enough; this crew member suggested 3-4 heat ranges cooler (?).

My observation was that it seems that when the missfire occurrs, the engine still runs pretty good... it seems like just one cyld is effected kinda like it's hitting the soft rev limit on that cyld. Since the OEM coilpack runs 2 cylds, you'd think that the car would really run bad if it were a coilpack (?). I wonder if this is perhaps a fueling problem? Do the injector harnesses often give you trouble?

BTW: What heat range and gap are recommended?

 

1 heat range colder is fine. Tons of people run those. Intermittent misfires are the devil to find. Took me 3 months to find my last one. Turned out to be a loose crimp in my ignition harness.

My advice is to figure out how to repeat it. Preferably on the street. Once you do that you can start diagnosing. Otherwise it's just taking shots in the dark.

 

How long of a session can datalog on TS? Is it normal to turn it on for a 20 min track session? Or, do you just start/stop it when you get to a point of interest?

 

The default logging profile (which is literally everything, at about 15 records per second) on my MS3Pro generates files that are somewhere around 28MB per hour. Fuel will limit how long you can log, not file size.

 

Are you coming to BMW day on thursday? Logging a whole session is no problem. Hardest part is finding a safe place for the computer.

 

Possibly use SD card?

 

No, but I did license and insure the car last week so that I could do a shakedown cruise before last weekend's race. ...I actually forgot how fun it was to drive the car on the street.

I'll be able to hook up my tablet and try to get some info up online soon.

I'll probably try to fix this myself... and if it goes as usual I'll waste money changing out needless parts, spend hours chasing down potential diagnosis, bloody a few knuckles, and then bring it into a professional like Curly to get it fixed right! But, maybe I'll learn something along the way.

 

You need the RTC module to do that.

 

No you dont.

 

If you want useable logs with timestamps you do.