Disconnected battery and now wont idle..help

Jeez!!!! The ECU needs to relearn. You don't have to drive it right away. Start it hold the gas pedal to keep it running. Let off the gas a little. If it starts to die, push the gas pedal a little. Eventually it will learn enough to stay running while you drive it. Although running a battery completely dead can shorten the life of the battery, if it has enough cranking amps to turn the starter, it's probably fine. Do not replace it just because the Ecu hasn't learned idle speed. Do not take the alternator off, and for Fucks sake, never disconnect the battery with the engine running. That's a good way to fry a bunch of very expensive electronics.

 

This was the video I found, does this make any sense?

https://www.youtube.com/watch?v=JCoAabBhRLw&app=desktop

 

Aside from the charging issue discussed above -
Completely removing power from the truck's computer for a period causes it to "re-boot" when reconnected. The engine tuning returns to original and it begins to "relearn" the operational parameters. Can cause some poor idle and rough running for a bit while it settles in.

Because the knock sensor steadily "detunes" the timing based on the worst gas you ever put in the tank - fuel curves for idle, cruise and so-on .....the reboot can be beneficial...... You would think that the automotive electrical engineers would learn to build a system that learns and keeps trying to upgrade performance when possible.

 

The ECU has a flash with the basic operation of the engine saved in. It should not die without manually keeping the engine speed up. The learning typically involves watching and adjusting Fuel/Air mix and learning your driving style. If OP is still experiencing this issue after maybe 5 minutes of the enging operating manually or not I doubt the ECU is the issue.

 

This is the first time I've seen an ECU have a relearn so bad that it kills the engine.

My Civics and my wife's santa fe don't have it this bad.

My 08 had it's battery out for almost 4 straight days. When I connected it and started, it fired right up. No issues.

 

The ECU maintains the basic flash in a non volatile state. Then holds tuning and optimization in a volatile state. The tuning and optimizing is what you lose when the battery is out. If your flash gets jacked somehow you have bigger issues and the engine likely won't operate whatsoever. Shit I'm running NA with a SC flash from a previous owner. Have had the battery out all weekend and it ran just fine. Maybe a little rough on Accel for the first few trips.

 

Maybe the throttle body is so gunked up that out of the box idle parameters don't cut it.

 

OMG this thread

OP, start the truck pedal to the metal haha

 

TRD flash?? If so I would trade ECU plus cash with someone who got a magnusson supercharger. You sitting on unrealized gains yo

 

OP asks for help.

Forum gets on it


Ends up being a bad batt and alt.....lol

Hopefully it's nothing more than that cause I've never heard or seen an engine go crazy when an ECU resets itself for learning.

Also, what light did you leave on that drained your batteries to near 0v?

 

Like this guy?

https://www.tacomaworld.com/threads/ecu-swap-2013-tacoma.602328/#post-20267359

 

Clean the throttle body and keep driving it

 

@Rainmaker Well??? Don't leave us hanging. What's the latest?

 

Maybe he was on his phone and the battery died on it too. If that's the case he will need to re-tune the volume control by bringing the volume up to 20%, then to 0%, then to 50%, then to 0%, then to 100% and back back to 0% 3 times.

 

Lol yeah its the TRD Flash... If anyone is interested... Hopefully its not so gunked that the base flash can't handle it.

 

Next time, leave the battery IN and connected to the truck when you need to put it on a charger...

 

The relearning process takes way longer than 5 minutes.
I find that whenever you disconnect the battery, it idles bad for a few days.
Cold starts are fine, because it goes into fast idle, but when it warms up, then it can stall as its trying to find the right balance.
After a few days, everything returns to normal.
Our Subaru has exactly the same behavior.

 

@Rainmaker
Clean the throttle body. I guarantee thats what the issue is. The computer has learned to deal with the buildup on the TB over time. When you disconnected the battery the ECU went back to factory settings. Clean the TB and youll be good.

 

I got this.......looks like you need to just replace the engine. Just do that and it’ll solve your problems.