Why does my 99 Oldskeep dying in traffic?

Could be a alternator or battery. Measure the voltage at the battery with the headlamps ON - should be 12 volts with the car not running, and 13.7 to 15.1 with the engine running.

There is a You Tube Video you can watch
on GM Throttle Body disassembly

I would mail them away for testing & ultra-sonic
cleaning

Not likely the injectors are causing the dieing

Check for a worn timing chain & vacuum leaks

check for a vacuum leak . check brake booster for the leak by removing the hose and blanking it off then idle with you foot on the brake and see it the problem appears. Check for a problem in the needle and seat area of the carby

Check vacuum leak; I suggest scanned in order to know if some fault code is stored there.

Check the engine for vacuum leaks around the intake gaskets.Just spray it with carb.cleaner or brake clean while the engine is idling.While you spray around the intake if it is leaking you will hear the idle smooth out when you spray where it is leaking.Also check the egr valve and make sure it is not sticking slightly open.Check all the vacuum lines.Hope this helps.Good luck.

I am having a similar problem, but there is no check engine light. It seems that mine dies at the light or running, if the rpm's drop. I am wondering if the Idle air control valve is bad or possibly the ERG valve?

There's a slight anti freeze smell when you turn the heater on. All fuild r full just wander if the heater core leaking. nothing wet inside the car just a smell

Sounds like a bad vacuum leak. Check all the engine vacuum hoses, make sure none are broken/cracked/disconnected/missing.

sound like could be a vacuum leak check all vacuum lines air filter housing make sure no leaks check throttle cable

Hello;
It definetly sounds like a vacuum leak problem. The vacuum hoses are routed to perform various functions for the engine and transmission. They can be very difficult to track down. They are small diameter black hoses and start at the intake manifold (the source) and go to their respective locations.
They could be cracked, oil soaked, loose fitting, or disconnected to name a few problems to look for. Take it to a mechanic if you do not feel comfortable replacing the hoses.
Thanks;
Rich
RPM Northwest