VEMS disconnecting randomly from MT and LCD quirks (at same time)?

[NOTORIOUS VR]

Hey guys,

I have an issue happening to me on a car, seems that randomly while driving the LCD will go all screwy and garble the numbers around and make the LCD screen look all messy.  At the same time that this happens, if I'm connected to my Laptop and in MT it will be disconnected and won't be able to reconnect unless I restart the car (ign cycle on/off).

I pulled out the ECU and checked all ground and power connections.  I checked the log file(s) that were running when it happened.  Nothing strange happens to the car (or shows in the logs for that matter, the log just ends clean as if I turned off the logging) and the car continues to run flawlessly.

All grounds on the ECU are good... checked all pins for the COM port as well... everything seems alright (approx 1ohm resistance from end to end).

I thought it might be my laptop causing it, I left that unplugged but I was able to see the LCD screwed up so I know the same thing happened.  Then I thought it might be the LCD, so I disconnected the LCD and just plugged in my laptop w/ MT on, and same thing MT disconnected after a while.

It is random though, it doesn't happen at the same time every time.  Also it doesn't happen if the motor isn't running (I left the ign switch on for about 30 min and MT and the LCD were fine), and it mainly happens within the first 2-3 mins of driving.

Spec's of the car:
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 1.0.73 16x14 tables
Electromotive 3x2 DFU's
Stock 60-2 crank trigger, no cam sync.

I will post up the config & log file later tonight as it's on my laptop.

Thanks!

-Sascha

[NOTORIOUS VR]

Alright, so I took the ECU out of the Corrado and put it into another VEMS'd car and I don't have any issues with the PC connection so that clearly points to a wiring issue somewhere in the Corrado

Gonna re-do all the grounds just to be sure even though they measured out ok with a DVM.

[dnb]

Sounds like a ground issue to me.

Do you have a PS2 keyboard connection?  If so, it's worth grounding the data line when the keyboard is not in use.  My ECU used to pick up noise this way - it took ages to track it down.

[NOTORIOUS VR]

Sounds like a ground issue to me.

Do you have a PS2 keyboard connection?  If so, it's worth grounding the data line when the keyboard is not in use.  My ECU used to pick up noise this way - it took ages to track it down.

good to know, but no I don't order my ECU's with PS2 connections anymore... never used em lol..

I'm gonna go over the grounds this weekend and hopefully resolve this issue once and for all... what a PITA this car has been to me.

[rob@vems.co.uk]

The only use I could think of would be to use the wheel speed input.

[dnb]

But the PS2 still has headers on the board which can pick up noise...  Granted, it will be nothing like as good as if it had an "aerial" attached!

[NOTORIOUS VR]

So I ended up pulling off the main/sensor ground and re did the connections to that pin (chassis side was good) even though everything measured out good with a multimeter...  And the problem is solved!

Man this car has been a real pain in the arse lol...

thanks again for the tips guys (btw, I didn't ground the PS2 header but I'll keep it in mind).

Cheers
-Sascha

[mr_g]

low-z injectors on PWM makes a lot of noise... I have high-Z, and also after a few minutes of harder pushing would loose the LCD until restarting of the VEMS..

[MWfire]

low-z injectors on PWM makes a lot of noise... I have high-Z, and also after a few minutes of harder pushing would loose the LCD until restarting of the VEMS..

bad wires and gnd.
So far in 1 year with low Z injectors(pwm) not a single problem with lcd. Lcd is connected with utp cable(no shild).