Need some help... Getting backfire due to ignition cutting out??

[NOTORIOUS VR]

I finished an install of a VEMS V3.3 on a Corrado VR6 Turbo a few months back. I successfully tuned the engine on the rolling road up to 8psi. I did not notice any erratic changes while driving. But customer says that while he is driving at a constant speed/throttle the car will 'turn off' and then after a few seconds resume with a loud backfire the engine will resume again.  I have since then driven the car for myself and felt this.

The ONLY was to correct this (or better to say to get the injectors to come back on) is to push in the clutch to return the engine speed back to idle.  You can then immediately resume back to normal cruising engine speed until it randomly happens again the next time.

All this only every happens during small/constant throttle movements (ie constant city driving and/or highway cruise situations).  If you're constantly varying the throttle the misfire never happens! 
 
Now I have had this issue once before on my friends BMW. At first I thought it was the RPM sensor (VR) and or the wiring, so the sensor was replaced with a brand new unit, and the shielded wire from the VR sensor plug back to the ECU with new wire. The problem still persisted. What I did to get rid of the issue was to load an older MSQ file and that made the problem go away. At that point all I did was import the VE, IGN, and LAMBDA tables into the older MSQ and the car ran fine after ever since.  Firmware of the BMW was always 1.0.73!

I also have this EXACT same issue on another VR6 Turbo car.... I don't get what is happening here.  I will admit both VR6 turbo cars are running 1.0.78 firmware w/ 14x16 tables.  But like I said above with the BMW that happened to develop this issue on it's own somehow it was only ever running FW 1.0.73.

Now last friday the Corrado wanted to be tuned for higher boost (approx 500whp), so we strapped it onto the dyno and I began to tune, but I was having massive driveablilty problems on the dyno, MegaTune was randomly freezing (I believe during the driveability problems) and also the LCD screen would go all funny and either show normal values with gibberish or normal values just moved all around the  screen and the WBO2 would no longer work and just show ??.? until the next restart.

Here are specs for the Corrado:

9:1 CR
forged pistons/rods
GT4088R turbo
3" turbo back exhaust
86# LOW-Z Siemens injectors (using 2x Honda Resistor boxes)
VEMS V3.3 w/ 30V flyback running 1.0.78RC2 16x14 tables
Electromotive 3x2 DFU's
Stock 60-2 crank trigger, no cam sync.

Here are the specs for the 24V VR6 Turbo that is also having the same issues (but much worse IMO - as in more frequent):
9:1 CR
forged pistons/rods
GT4094R turbo
3" turbo back exhaust
89# LOW-Z injectors (using 2x Honda Resistor boxes)
VEMS V3.3 w/ 30V flyback running 1.0.78RC2 16x14 tables
Electromotive 3x2 DFU's
Stock 60-2 crank trigger, no cam sync.

So two very similar setups, injectors are slightly different though.

Also I have noticed that during logs I would sometimes get a zero (0) RPM blip as if it's loosing the trigger... but the car drive fine otherwise and never shows trigger errors otherwise.  Polarity is correct on the VR sensor on both counts because reversing them will make the car not show RPM signal at all.

Here are a few files from the dyno run with the Corrado:

MT Log:
--RPM blip to zero happens @ 99.202 sec
http://www.vems.hu/files/MembersPage/Sascha/HIBOOST/hiboost-3.xls

MSQ:
http://www.vems.hu/files/MembersPage/Sascha/HIBOOST/dyno%20tune%208psi%20-%20306whp+%202step%20active.msq

Config & Tables:
http://www.vems.hu/files/MembersPage/Sascha/HIBOOST/config.txt
http://www.vems.hu/files/MembersPage/Sascha/HIBOOST/tables.txt


And finally my (seemingly useless) Wiki page:

http://www.vems.hu/wiki/index.php?page=MembersPage/Sascha/HIBOOSTCorrado

I really need some help on this, so any input would be great!

Thanks,

Sascha

[gunni]

First I thought it would be the overrun and overrun resume,
but that log doesn´t really show it enough.

Can you get a log with more occasions?

[NOTORIOUS VR]

^^^ I thoguht so too at first, that was actually something that I tried right away...

I almost think it's a rogue config setting somewhere.  Yesterday I setup a VEMS in my friends Audi (V6 2.7T w/ single turbo) and the VEMS that is in it is from another friends car (Turbo Porsche 928) which is a V8.  I couldn't for the life of me make the car run properly by changing the settings through MegaTune.  I don't understand what it was... The tables at least looked correct to me and I'm 100% sure that it was the fuel injectors that were not firing properly.  This was on FW 1.0.73 with 14x16 tables.

Anyway, I don't currently have any other logs that I can think of... I'll have to dig around some and I might come up with some from my friends 24V VR6 Turbo that also has this problem.

Let me see what I can find

--Sascha

[NOTORIOUS VR]

Welp.... I fixed it.

It seemed to be something in the config I believe.  I just started from fresh.

Loaded 1.0.73 14x16 tables, and then started with a fresh config.  Bam no more cutting out.  Lesson learned.   Make sure you have a clean config!

Now I have another issue though

the ECU seems to be disconnecting from my laptop (MT) and the LCD screws up at the same time.  Gonna start another thread for that.

[MWfire]

Welp.... I fixed it.

It seemed to be something in the config I believe.  I just started from fresh.

Loaded 1.0.73 14x16 tables, and then started with a fresh config.  Bam no more cutting out.  Lesson learned.   Make sure you have a clean config!

Now I have another issue though

the ECU seems to be disconnecting from my laptop (MT) and the LCD screws up at the same time.  Gonna start another thread for that.

you need to use shillded cable for lcd and laptop. You have many electrical noise, probably poor ground of bobbin.

[NOTORIOUS VR]

you need to use shillded cable for lcd and laptop. You have many electrical noise, probably poor ground of bobbin.

Strange I've never had to use a shielded cable for either.  But it's something to consider.  That said, it's neither the LCD or the PC connection that is making either/or screw up IMO.  It must be something else.

Also this problem existed with the previous firmware version as well, I see now that I made it sound like the other problem went away and this one appeared, which is not the case.

[lugnuts]

I didnt read any of the above, but heres a tip:
Check/disable your WOT Shift-Cut function.

If there is no pull-up resistor, this will cause random ign/fuel cut-outs if it is enabled.