Engine shut down while running.

MurrayA4 · Post by **MurrayA4** » Sat Apr 08, 2006 5:21 pm

I'm in the tuning phase with my MSII V3.0 running 2.3 code I'm running fuel only for now and am very pleased with the progress I'm making using Autotune. I went for a run today and on three occasions my engine shut down. Now I'm trying to figure out why.It happened under different circumstances ie:full throttle accel,coast down and just cruising.I've attached a piece of my log which shows a loss of RPM and TPS signals.Anybody have any ideas what is going on here and where I should start troubleshooting ? Up until today the car has done maybe 300 miles with no such problem.Wiring has not been touched and the only changes made were reducing the O2 lagfactor from 50 - 40 and whatever changes (minor) Autotune has made to my VE table.

MurrayA4 · Post by **MurrayA4** » Sun Apr 09, 2006 3:23 am

Last night I was going through my datalog trying to get a handle on this problem and I noticed something weird.The value SecL in Megalogviewer, is it not supposed to go from 0-255 and then restart ? Mine continues to climb unless I experience the engine cutoff described above.I'm seeing values like 866, 745 etc.

MurrayA4 · Post by **MurrayA4** » Mon Apr 10, 2006 8:16 am

MurrayA4 · Post by **MurrayA4** » Mon Apr 10, 2006 1:22 pm

Lance yes I've upgraded the code to 2.35 on my MS II V3.0 board.My ignition is stock Bosch and I'm using the coil negative for MS trigger running fuel only.I know you must get sick of looking at other people's logs but on the one I posted the dropout is at 3020.531s.

Do you have any thoughts on the Secl issue I mentioned above ?

In trying to narrow this thing down I may have come across a possible solution.When I looked at my VE table in 3D I noticed A major peak at 3500rpm 65kpa.It seem that my Autotune has performed major surgery on all the points around and left this anomoly.Could running into a very rich point relative to all the surrounding one's lead to a reset ?

MurrayA4 · Post by **MurrayA4** » Mon Apr 10, 2006 4:16 pm

lance wrote:MurrayA4,

At the point you mention (3022.254) there's the end of an accel event, then a reset. Was the MegaSquirt left running at this point, or was the power cycled to restart the engine? Do you have decel fuel cut enabled? It may be too much and is causing the engine to stall.

- At that point (3022.254) the engine stalled and I turned off the ignition and restarted - while rolling.
If by "decel fuel cut" you mean "Decel Fuel amount" I have it at 100%

It's certainly possible for autotune to mess up the VE table, and it should be used sparingly, and with a lot of 'adult supervision' to make sure things don't 'go off the rails'!

Interestingly, though, the CLT temp also takes a sudden 2.2 degree drop at the rpm drop-out point, which makes me think the grounds may not be 100% perfect too (it could be normal cooling too - there is a 1.5 second gap in the datalog, which doesn't seem enough, but I couldn't say for sure...).

-All my grounds are solidly bolted to a clean point on the chassis,but if you think that may play a part I'll run a line to the battery neg.

I don't see any secl values greater than 255, but I may be not looking closely enough. If these are occurring, they almost certainly result from communications errors. Are you using a regular serial port or a USB/serial adapter? What do you have set for the 'timer interval' under communications?

- On the piece of log I supplied the reset occurred at 237 Secl so the higher values, don't show however on the complete datalog they go up to 566.On some logs they go as high as 1202.The Secl stops rising as soon as the engine cuts out.I'm using a usb-serial port with timer interval @ 50 ms.Lance.

MurrayA4 · Post by **MurrayA4** » Tue Apr 11, 2006 4:41 am

Lance it just gets weirder.After reviewing your comments in the e-mail you sent I decided to look at another log file in Megalogviewer.I used the "Example MSII log" that comes with the Megalogviewer download and the Secl count reads up to 925 so it would seem that this value (Secl) does not follow the 0-255 count from the processor ?

MurrayA4 · Post by **MurrayA4** » Tue Apr 11, 2006 9:09 am

Ok thats a relief at least

I ran the car today without MT running and same problem so I started MT and logged again.What I noticed,and this shows on the log I already posted above, is that just before the cutout something is driving my AFR signal to beyond lean - 25.30-I'm running an innovate LC-1 so I removed it from the exhaust and re-calibrated everything. Re-installed and voila the same thing.I have set my .ini to both LC-1 and generic wideband to try and eliminate this all the while properly calibrating my AFR in "tools" and no change.