Didn’t know this: That’s actually a pretty classic symptom of an AGM battery swap in an older vehicle. A few likely reasons:
The ECU/PCM needed to relearn its idle and fuel trim settings. When you disconnect or replace a battery, the Toyota ECM loses its adaptive memory — fuel trims, idle air control position, throttle position baseline. On a 2005 Camry, it can take several key cycles and a few drive cycles before everything normalizes. The stalling during cranking/startup is consistent with that.
Voltage behavior difference. AGM batteries deliver voltage slightly differently than flooded lead-acid during cranking. Some older ECUs briefly “read” that as a fault condition and can stumble until they stabilize their voltage reference points.
Throttle body relearn. Toyotas of that era are known for needing a throttle body idle relearn after a battery disconnect. The idle air control system essentially has to find its baseline again. The multiple start failures could have actually been the system cycling through that learning process.
What likely happened on start #7: By that point the ECU had enough data to reestablish its idle, fuel trim, and throttle position baseline — so it just started running normally.
One thing worth checking: Make sure your alternator is actually charging the AGM properly. The 2005 Camry’s charging system wasn’t designed with AGM in mind — AGMs prefer a slightly higher charge voltage (around 14.4–14.8V) and some older alternators run a bit low. A quick voltage check across the battery while running (should be 13.8–14.8V) will tell you if the alternator is keeping up.
If it starts stumbling again, the Toyota throttle body relearn procedure (ignition on/off cycles with specific timing) is worth doing intentionally.
So apparently it is pretty common - was scary when starting it up and it kept dying…
I know modern ICE cars need to be “reprogramed” to accept a new battery. I had a mini and learned the hard way, changed the battery and within a few days the new battery was dead.
I would take it to a shop, they may need to tell the cars computer you need a new battery. The last BMW I had was the same. Expensive to replace a 12v battery these days.
Also, have an EV and I am never going back to an ICE vehicle. Basically zero maintenance. Plus I run it for free practically. Charge at home that has a solar system.
Camry running great again - getting the headlights replaced at 10am Today…
After 21 years the plastic is cloudy and yellow from the inside and out..
Tried those lens polishing kits - did not work enough…
We shall see - I hope to keep the car another 5-7 years and need to be able to see at night…
The front bumper has to come down to install the new light housings - kind of a bigger repair…
I would not have kept the car - but found a traveling certified mechanic - he has done all the repairs and recommendations - especially the struts - shocks - and sway bars…
Buying quality parts and his expertise has let me keep this car for many extra years…
I would guess $2000 in all the parts over the years he’s been doing my car…