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Discussion Starter · #1 · (Edited)
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,
Jason
 

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similar problems for many other people

http://www.yoursciontc.com/forums/8...94-idle-problems-after-i-changed-battery.html


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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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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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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wow scared me! I'm not a Mechanic at all!! If it weren't for forums and YouTube I would be paying someone. I changed the O2 sensor and plugged battery back in and almost shit me pants! Thanks for the heads up!!
 

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I am having the same issues with my 08 Scion tC sputtering and stalling after disconnecting the battery to change the spark plugs. I’ve drove it for about 30 mins and kept the ac blasting and it still has not adjusted the idling to its normal self. This seems to be a normal thing for Scion tC’s?
 

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Ok so what would you guys think my problem is with my 09 tC? Battery dead the other day...charged it and it was driving normal for two days. Then today got to store, was in there for 10 min and went out to dead battery. Got a jump and drove home and took battery out and cleaned terminals and such bc had a bit of corrosion. All clean and battery back in and wanted to die but I kept it going. Stopped at store for about 20 min and it Started up with a little Dead batteryish hesitaion. Sputtered and stammered all the way home and in driveway I wanted to see how long it would stay running without pushing gas and it died before a minute was up. Tried to restart and battery was dead. I have replaced alternator last summer so idk why it would be that again and plus none of my light have been dimming or flickering. But I guess it could be but does anyone have any ideas what it could be besides replacing the battery probably? And also I had no warning light. No battery light... Nothing but the seatbelt light and dinger still going off? Is that weird or just me overthinking?
 

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Test the running voltage at the battery to determine if it is charging correctly. If so, have battery load tested to see if the battery is good. If both are good, time to do a parasitic load test on the system to see if there is abnormal current draw when the car is off
 
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