Intermittent Stalling Issue

Hey everyone. I've been having a random stalling/hesitation issue for the past 2 years that I just can't figure out, and I'm hoping somewhere here can help me think of more things to try. I'll get straight into the details...

Truck: 2001 single cab, 4x4,, automatic, with stock 3RZ, ~250k miles
Issue: truck will either completely stall, hesitate, or feel like it will stall, then catch itself
Frequency: this can happen multiple times in a single drive, or once in 3 months
Conditions: I live in Southern AZ, but this seems to happen in any weather, and at any engine/running gear temp. I mostly have the issue when shifting into drive or reverse, slowing to a stop, or when just stopping. I do occasionally get hesitation while accelerating or holding a steady speed. It has never stalled just sitting at idle, and the truck always starts up the first time, with no extended cranking.

I've taken the truck to the dealer multiple times with no luck on a cause. I have gotten codes for the MAF sensor when this happened before, but haven't had any in probably a year.

So far I've done: both O2 sensors, MAF twice, spark plugs, Toyota dealer fuel injection system cleaning, fuel filter, Toyota dealer verified fuel pump is in spec, throttle body cleaned, IAC valve replaced, TPS replaced, replaced vacuum hoses that looked old/cracked, vacuum switching valve replaced, coolant temp sensor replaced, valve adjustment checked (shop said all were perfectly in spec), every fluid in truck replaced, and dealer checked for bad grounds. All parts were Toyota branded or the OEM.

I'm honestly considering selling the truck because I've just been so frustrated with this issue. Everything else is fine and it drives great when this nagging issue isn't around. Any help here would be greatly appreciated.

 

Next time she stalls hopefully she wont start right away, then check for spark out of the distributor.

 

Mine has the newer setup with coil-on-plug. But maybe ignition could be the issue.

 

Just wanted to report back that it looks like I’ve fixed my issue. I replaced all my coils, as well as switched to OEM plugs, and the truck is driving a lot better and hasn’t stalled or hesitated once.

The plugs were fine, but it looked like the coils were original to the truck at 258k miles. They held out for quite awhile!