Low Idle/stall after battery unplug - Scion tC Forums
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post #1 of 5 (permalink) Old 04-05-2012, 06:19 PM Thread Starter
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Default Low Idle/stall after battery unplug

Hey guys,

I've run around these and a few other forums looking for answers and I can't seem to find anything concrete.

I just had to replace the positive leads to my battery (2005 tC manual trans.), they got pretty corroded. Had a slight issue with the wondow not working, ghost in the machine I guess, works fine now.

But here's the concerning part: When I turn the engine over, it RPMs up like normal then drops to zero and stalls out. Turn it over again and it runs, but at a really low RPM and if I clutch in too fast, stalls out again. I've disconnected the battery to try to reset and it still happens. If I allow it to idle at a higher RPM by holding the gas in a bit, it seems to get better after a few minutes, but it's still a bit low (600-700 RPM idle)

I plan on soldering the leads to make sure it's a very strong connection, but it looks good (everything else works on battery power too: radio, sunroof, driver window, lights, alarm, etc.). Autozone did a battery check, and it's strong.

Some forums say clean the Idle Air Control Valve, another says we don't even have one and that the ECM controls everything. I might try cleaning the throttle body too? I've got a long drive this weekend for easter, and I'd like to not be stranded in the desert. Your thoughts are greatly appreciated.

Thank you,

Last edited by jasonpedersen; 04-05-2012 at 06:31 PM. Reason: Window issue resolved itself, weird
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post #2 of 5 (permalink) Old 04-20-2015, 05:44 PM
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Default similar problems for many other people


I had the same problem after changing battery too. Pretty bad. Would bog and stall even after many miles of trying my best to keep the RPMs above idle.

I don't understand why, but blasting the AC speed up the process by which your ECU is learning and adapting. I was frustrated by how long it was taking for the ECU to learn until I blasted the AC and it immediately bumped the idle RPM just enough to keep the idle from stalling. Then the car immediately went from rough idle to smooth idle. A few miles of driving with no stalling and my TC was back to its old self.

I'm pretty sure if I looked at my throttle bodies they would be filthy and my ECU is guessing how much air it needs at idle but isn't feeding enough of it. The ECU has adjusted by now.
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post #3 of 5 (permalink) Old 03-08-2016, 01:01 AM
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I had this same problem on my 2007 scion tc. Dude at Firestone said that with some Toyota vehicles after replacing the battery you need to let the car sit and run for 25 minutes than drive it two miles for the computer to reset. My car is driving normal now.
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post #4 of 5 (permalink) Old 03-10-2016, 04:59 PM
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All ECU equipped cars do this, to varying degrees. Just driving it long enough will fix it. On the tC, it normally takes about 20 min of driving for me, sometimes more, sometimes less. Depends on how it is driven, etc.

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post #5 of 5 (permalink) Old 06-06-2019, 08:37 AM
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Thank you for sharing
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