First and foremost, thank you for reading and thank you for the info in advance!

2003 v8 with 205k miles. Driving a few weeks ago (in very hot weather) and while stopped at a light my check engine light started flashing and my vsc trac lights came on. I turned my AC off and the engine light went from flashing to solid. Plugged in a code reader and it came back with all cylinders misfiring. cleared the codes and did a zero point calibration on it to clear the vsc lights. Was good for aboit 2 weeks.
Went to go start my car after a few weeks and the car didn't start. Dry cell in battery so put a new one in. Everything was still good.

A few days after a new battery, I was sitting t another light with the AC on and the same thing happened. The engine starts to vibrate a bit more with the AC on and the check engine light started flashing again as well as tripping the vsc lights.

I'm kind of at a loss as to where to start looking. Seems that running the AC in the hot weather is doing something and the computer is wigging out. The truck seems to be running ok.... I don't notice anything drastically different other than a bit of loss in power during these hot days. Any idea where to to look would be helpful. Has anyone had this happen to them?

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I know that the CEL flashing is indicating something REALLY bad is happening. This past weekend I accidentally drove into the ocean and got saltwater in the engine which caused some backfiring and the CEL started flashing until all the water dried up. The CEL has never flashed on me before, but I remembered that it was really bad and stopped the truck that evening before anything terrible happened.

Never encountered a flashing CEL before, but it appears to correlate with misfire conditions based on these posts.

Not sure what the AC would have to do with it, but if you haven't gotten water in your engine, I would start with checking spark plugs for fouling and making sure you don't have a radiator leak, perhaps getting the fluid level checked and getting it pressure tested.

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A blinking CEL indicates a misfire condition that could damage the catalytic converter. It's a good idea to stop the vehicle as soon as safely possible to avoid damage when your CEL is blinking.

The VSC/stability lights will ALWAYS come on when your CEL is on. Performing a zero point calibration wasn't needed. In this case, clearing your CEL is what also cleared your VSC/stability lights.

A random misfire across all cylinders could be caused by lots of things. Since you only got a misfire code and nothing else (like a bad sensor), I'm putting my money on a fuel problem--I bet your fuel pressure is low.

If your scan tool shows live data, you'll have a lot of data points you can look at to help point you in the right direction.

Good luck.

bro, you can't just leave it at that.

Ditto...

Ok so it was at Pismo Beach on Friday night, I have never seen it that crowded before as I was just trying to leave. People were camped shoulder to shoulder but then parked all their cars literally in the waves and the only way to get out was to drive out into the deeper water and around them. I thought I had timed the waves right and went between two small waves, but a rogue wave came up over the hood and onto the windshield a bit. I turned the truck to the shore and just started heading to the exit when I heard some crazy backfiring and saw the flashing CEL.

I can relate. LoL Last time I was at Pismo, high tide filled up the entry/exit way and many couldn't leave. Everyone parked and people lined up around the water pool. Me and my buddy said f**k it. My buddy drove thru first and I can see the water above his fender. We both drove thru it as crowd of people cheered us on.

Then a couple weekends later, I blew my transmission seal there at Pismo. And so a used transmission took it's place. My post is somewhere on here. LMAO......wife is still bitter..

i threw in a can of injector cleaner in my tank, and problem solved. something similar
has happened to me 3 times now. though without the flashing cel.
low rpms, vibrations, mil lights, p0300 code - random multiple misfires, vsc

Thanks for the help guys. Ya it only happens when the AC is running, I'm stopped, and it's hella hot outside. I parked it for the night went to go drive it the next day and the CEL light and vsc lights were off. I didn't clear them or anything. So weird. My fluid levels are good. I haven't checked my plugs yet but I don't really think it's a plug since it only happens under specific circumstances. Could a bad CAT throw those codes? I have had a loud clapping sound coming from the muffler for a while but never caused any issues. Figured it was a leak on the pipe or something

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I'm having the same issue - even posted my own thread about it. Misfire on all 8 cylinders - 2004 Ltd v8

Update:
I took it to my trusted neighborhood mechanic and after checking the fuel pressure and condition of the plugs, he explained that he thought it was an issue with the engine compartment getting too hot and wigging out the crankshaft sensor. He also noted that the radiator could be gunked up inside and causing an overload on the system. I had him swap out the radiator and put in a new crankshaft sensor and well, the CEL still comes on after a few mins of sitting idle with the a/c on. I'm taking it back to him tomorrow to see What he says but I'm back at ground zero.

A buddy of mine has a brother who uses to work for toyota and he said it could be that I could have a small misfire going on that isn't being detected by the computer but once I crank the ac , it causes the misfire to worsen and sets the CEL off. I don't think that's the issue but I'll bring it up to the mechanic. So wack

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My concern is that original poster said battery was dead and replaced the battery I recently had all the same symptoms turned out my alternator was cooked since I replaced haven't had any issues (I also replaced the battery too) hope this helps check and see what your alternator is doing

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What DTCs did/do you have?

Just out of curiosity, what is the voltage of the battery when this is happening? When my alternator crapped out, my transmission started shifting funny and the dash lit up like a Christmas tree, except for the battery light ironically. My voltage was at 10.9 volts. I was able to make it home on my Aux battery, but low voltage or even a bad ground will cause weird stuff to happen. According to the Toyota service manual, the alternator should be putting out 13.1 volts or greater with headlights and AC running.