ECM trouble

[84 BuickGNYorkPA]

I pretty much have a backup to every part on the car, and glad that I do, much quicker to get it back on the road.
After work last week, get on the road and car stalls less then .5 mile from the parking lot at work. So I turn the key off, pop the hood, turn the key back on and see that I have fuel pressure. Get back in car and turn the key off, pull out my Turbo Tweak Speed Density cheat sheet, and check 1st parameter. This is the WOT parameter and I have mine set to the default value of 128, but what do I see? A two digit number, 65 so I attempt to set it and find that the parameter won't respond to the gas pedal at 1st, then there is a long delay and suddenly the value becomes 93.... eventually I go through all the parameters and get them set. I turn the key and the car starts and idles fine, a couple of hits with the throttle and all seems well. I get about 300 hundred yards and have to stop at a traffic light, light turns green eventually and car bucks/backfires, I let it idle and  pull over into a parking lot and I'm able to back into a space. I recheck the parameters and some are off again, but not as drastic, same thing reset them and make it home(about 10 minutes away). I ignore the car for a few days as my schedule is busy with other obligations. I pull the ecm yesterday, and of course with the Speed Density chip and power logger (computer piggy back board) I'm always skeptical that the piggy back power logger board slid down and I was losing contact(s), but I find that my board is still up all the way and good and tight(thanks to the velcro strip still holding strong). Still not sure if it is a problem with the power logger board itself, the scanmaster or the ecm, I change out the ecm with my used spare ecm that I picked up for $20 last yr . Sure enough I had to run some errands yesterday and the Buick ran great, and before I fired the Buick up, I went through the chip parameters and some had lost there value and others where at there value I had set earlier.... I guess I need to get another ecm for my back-up stash...
Any thoughts? Thinking of buying a reconditioned one from Advanced Auto or Napa and putting that one in the car... no that may not work, I believe they have a seal on them and if I open it up for the power logger card, warranty will be out the window...


Chuck

[Steve Wood]

Not sure that is an ecm problematic.

[daveismissing]

I see no problem paying < $50 for one from an xfi upgrader personally.

[84 BuickGNYorkPA]

Just out today with the car again, probably put 30 miles on it since the ecm swap, and so far not a hick-up.  I like the idea of looking for another used one for under $50 as a "new" spare. Before when I had a issue with the parameter value changing, the power logger board was not staying in place, on the main computer board, some fresh velcro strips fixed this issue.


Chuck

[Steve Wood]

PL will cause strange things if pushed all the way onto the connector at times..just like DS

[SuperSix]

PL will cause strange things if pushed all the way onto the connector at times..just like DS

Good to know!

[dennisL]

I agree with Steve in that a bad ecm would show different symptoms.  Its strange that your setting changed, but not to the "reset" value of 128.  When the standby power (orange wire at battery) is interrupted, the ecm resets all the blm cells to 128.  Also, a power reset would cause the SD chip to put default values in the blm cells.  From what you said that didn't happen.


My guess is that somehow PowerLogger changed your blm.  That's the only logical explanation for numbers like 65 and 93 for the early wot fuel setting.


Was it just the 1st & 2nd WOT Fuel parameter that went "bananas"?


If it happens again and you can't determine the cause, as a last resort I could modify your SD chip to make sure the blm values stay within range.  I could also change the default values to your settings so a power reset restores your numbers.  To do this I would need either your chip or the chip's bin file from a prom reader.  You'd get your chip back plus the modified one. (Just something to consider.)


Dennis

[SuperSix]

What a great group of members we have here.

[daveismissing]

I've always tried to hang around with smart people, that's why I'm here.

Hoping some day some of it rubs off....

[Steve Wood]

Seems like Eric mentioned a potential cause for such things

[84 BuickGNYorkPA]

Dennis L,


Thanks for the offer, but I believe that I will be ok.
The SD chip retains it's memory every time the key is turned off, let me get a quote from TT forum. " The SD chip will remember all your
settings using the Powerlogger’s memory, so they will not be erased if the ECM loses power. If
you want to reload the chip’s default settings, see parameter #21."
Eric has it flashed pretty close, I actually lean out a few of the settings and add some timing.
So I've had the SD chip installed over 3yrs now and never experienced the SD parameter being lazy like that before... there is one test that would put this to rest.... re-install the questionable ECM that I just took out. But it's a PITA to pull the ECM and take it all apart to swap out the PL board... not to mention doing this along the road..if it would let me sit again.


Chuck 

[Steve Wood]

Again, I think I have seen Eric make mention of such strange  numbers, but, I am probably wrong

[dennisL]

Chuck, if you still have the "bad" ecm out of the car, look closely at the edge connector pins where PL attaches.  Use a magnifying glass if you have one.  Check if the gold is scratched off any pins.  You can also clean the pins while you're there which could possibly fix the problem.


I know PL saves your changed settings but I don't believe that a power reset is your problem.  Especially since the setting that changed was supposed to be at 128 (default).  I dunno...


Dennis