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Is there any way to flash the onboard computer with new defaults for idling?

Old Oct 30, 2018, 12:17 AM
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Is there any way to flash the onboard computer with new defaults for idling?

So Ive read that the defaults in the computer are great for a new car, but as the car gets older and older the computer compensates for the car getting older and adjusts how it idles. So then when you replace the battery and you end up resetting back to defaults, all the learned stuff is lost and your car starts stalling when idling until it re-learns to compensate again. So I had to disconnect the battery to clean off the corrosion on the positive post earlier today. Now its stalling like crazy if I dont press gas.

So the question is. Those factory defaults are useless on this car, they will never be useful again due to it no longer being a new car (car is approaching 100k miles, and its turning 16 years old this month). When it re-learns again, is there any way to re-flash those values as new defaults?

EDIT: Managed to re-teach it. For anyone that stumbles upon this here is the procedure (done on 2003 Lancer ES 2.0L all stock):
1) Let the engine cool down all the way, for me this was 2 hours with ambient temp in the 60's F (~15 C). (If you do this on hot engine this wont work, you will only waste your time).
2) Before turning the car on, turn off everything (turn off lights, turn off fan, turn off A/C, turn off any chargers (phone etc), turn off radio, keep doors closed
3) Move key to ON position (dont start the car)
4) Wait 30 seconds
5) Turn on the engine and let it idle for 10 minutes (if after 10 minutes engine is not all the way warm yet, then let it idle until the temp gauge is at its normal max temp (around half way)).
6) If not already set, set parking brake
7) Keep your leg on the brake and switch to Drive and sit like that for 5 minutes
8) Start turning on devices (everything except A/C), radio, any chargers, headlights etc allowing 30 seconds in between.
9) Turn on A/C and idle like that for 5 minutes

You should be set. Turn off the car. Wait a minute and start it back up, it should idle without issues. It will keep learning, so RPM may still be lower or higher than normal, but it should no longer stall. And RPM should stabilize to normal after a few days of driving. If it still stalls, let it cool down all the way again and do the above steps again, this time idling for longer in each step.

Above worked for me. I was extra cautious with steps 8 and 9 as to not overload/kill engine, but in most cases those can probably be combined.

Side none: In most cases the computer wont be reset if a battery is disconnected for a few hours, some cars can be measured to still have small amount of voltage in them keeping RAM alive even when measured after leaving the battery disconnected overnight. To do a quick reset disconnect both leads from the battery (both positive and negative), and touch the two wires together. MAKE SURE NOTHING IS CONNECTED TO THE BATTERY because bad things will happen if either of the leads is connected to the battery when you touch them together. Touching them together drains the remaining small voltage in the system. This will reset the learning computer. Im not sure if there is any reason to ever do this. But thats how you would do it.

Last edited by Chrushev; Oct 30, 2018 at 03:14 PM.
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