Tune won't stick

240sx_god · Post by **240sx_god** » Fri Mar 14, 2008 1:35 am

I have an sr20det in a usdm 240sx chassis it has run fine for ~3 years and i have been succesfully tuning with the nistune hardwarer installed for ~8months.

Until last week, i was running z32 maf and 550cc injectors all was well and then the car started missing and afr's were all over the place in O2 flagged regions.

I pulled the ECU and wiring harness and discovered pin 17 (maf ground) had melted it's sheathing, I opened the ecu and D411 (a diode) had burned so i replaced the diode and connected the shielding to the chassis ground on the MAF

started the car and had to play with the K constant to get the car running of an old tune (went to about 140% to idle correctly) clicked apply burned changes to the ecu, went home and slept, woke up and started the car, it was back to not running right, so i opened the K constant and moved it again to ~140% clicked apply and burned changes turned it off and ten minutes later we're back to not running right.

Did I become insta-stupid?

Someone tell me what's up please.

Mike From San Pedro

Matt · Post by **Matt** » Fri Mar 14, 2008 3:04 pm

Hi Mike

I got your voicemail at work. Unfortunately I cant call overseas from here since the phone is blocked for international dial. Did you try and call last night 3am??! I only just got to bed before then

I'll email you tonight when I get back since it will be too late you call you by that time

Now what you have mentioned is really strange. The reason why, is that if there was a problem with the EEPROM part of the Simtek chips then the ECU should not work at all.

The EEPROM is copied to SRAM on each power up. The ECU runs from SRAM and can be modified on the fly (allowing for the realtime part)

The burn stores from SRAM back into EEPROM

So the changes you make are made to the SRAM and stay in there, but not saving to EEPROM?

That is very strange. I wonder if the problem took out part of the circuitry on the board?

We probably will have to organise a swapover board

Matt · Post by **Matt** » Fri Mar 14, 2008 3:11 pm

the other thing is:

started the car and had to play with the K constant to get the car running of an old tune

why did you need to pull back an old tune prior to the tune you were currently using?

240sx_god · Post by **240sx_god** » Sat Mar 15, 2008 6:27 am

I didn't call at 3AM I just called the once shoulda been ~9:45 your time

I got the ECU back up and running, Truthfully i couldn't tell you what the issue was, could have been the usb consult interface kept dropping off each time i asked to burn, as my usb consult cable has been giving me fits recently.

Matt wrote:the other thing is:
started the car and had to play with the K constant to get the car running of an old tune
why did you need to pull back an old tune prior to the tune you were currently using?

Because I was going back to old injectors (stock) so that i could have the others flow checked. I was having a lean misfire condition at constant throttle ~10% in the O2 flagged portions of the maps.

Thank you for your help and quick replies.

Mike

Matt · Post by **Matt** » Sat Mar 15, 2008 9:53 pm

Thats excellent. We were just about to shoot another board through to you. If it drops during the burn then it wont save at all

You would have just missed me on the way to work? Yeah didnt know who called at 3am... so I took my number off the orders page