Car stalling in traffic

Hope you have some ideas! I have a 2001 Saturn L200 that has been extremely reliable until recently.
My car is suddenly unable to deal with stop-and-go traffic. After sitting in traffic for 15 minutes or so, I will hear something that sounds like a fan or electric motor come on. It sounds like it comes from under the hood on the passenger side. Shortly after that, it seems like the accelerator stops working. I let the clutch out, and hit the gas like normal, and the car stalls. When I restart the car, the fan noise is gone and it runs fine for another 5-10 mins before it all happens again. This has happened maybe 4 times over the last few weeks. It has not happened under any other driving conditions.
Thanks for any advice!

Is the temperature in the normal range when this happens?
Perhaps see if you can duplicate it after the car is hot and parked in your drive way. See what that fan noise is – it likely is a fan but make sure it indeed turns on.

The car’s temperature has been right around midline when this has happened. It sure sounds like the fan, but I don’t understand why it would suddenly effect the car in that way.

Try getting it to fail in the drive way. Look to see whether the fan comes on.
Some cars shut themselves off when they detect an overheating condition. The thermometer on the dash may not necessarily get its information from the same source as the engine’s computer. It could be that the sensor is bad but you want to make sure you’re not oveheating as that could turn into an expensive problem.

This guess is a very, very longshot. But I’m going to suggest checking it anyway.

It is possible that the battery and/or alternator has become weak to the point of just barely being able to keep the engine idleing, and the sudden added draw when the cooling fan goes on is enough to kill the engine when you then try to accelerate…and that could be exascerbated by a binding fan that’s drawing an excessive amount of current.

In short, it soundslike the engine at idle is just barely operating.

How many miles does the vehicle have on it?
Has the maintenance been kept up to date?
do you have a Check Engine light?
Have you checked for stored codes?

Many parts stores will check out your battery and check for codes for free. i’d start there. And I’d get all the maintenance caught up.

Post back.

It has about 150,000 miles on it. The alternator was replaced about 40,000 miles ago. I’ll definitely get the battery checked. Decent but not meticulous maintenance, but I do get regular oil changes and tune ups. The check engine light came on just as I pulled up to my destination the last time this happened (about two weeks ago). It was off when I got back in the car and has remained off since then.
I’m not sure what you are referring to by ‘stored codes’.
I’ve not yet done a “fail test” in the driveway. I’ll do it after finals!
Thanks for the feedback and ideas, everyone!

Husband just reminded me our battery is about 4 years old. What’s the normal lifespan for a battery?

"Husband just reminded me our battery is about 4 years old. What’s the normal lifespan for a battery? "

This depends on where you live, how you drive, and the condition of your alternator.

If you live in a northern state, you should be able to get 6 years of life from a battery.
If you live in a southern state, you might be lucky to get 4 years of life from a battery.
However, if you do mostly short-trip driving, the life span could be shorter, as the alternator never has enough time to fully replenish the battery’s charge between engine starts.

And, if your alternator is weak, a brand-new battery could be dead within a couple of weeks.