I'm going out of my mind with this car. I just spent $400 getting a serpentine belt, pulley and compressor replaced 2 days ago. They tested the alternator and said it was good, battery is good, even checked the ground wire and it's good.
So what happens is - without warning, it will suddenly start acting like it's starving for fuel, like I'm running out of gas and I start to lose power BUT if I pump the gas pedal a couple of times then it stops doing it and acts normal. Feels like a fuel issue to me but I've had other people disagree and say it's electrical. Idk what to do. I can't afford anymore repairs. Any ideas or ways to check and diagnose the problem myself??

 

Are you receiving any DTCs? when was the last time the fuel filter was replaced? A faulty fuel pump or filter could present issues similar to what you've described, but the tools and process to diagnose are difficult and probably cost more than replacing the pump or filter themself.

Perhaps observe if the issue is present under certain conditions (like going up a hill, or when the engine is cold, etc) and report back?

 

Any chance it is Ignition switch issue known to exist on some 1999 TLs?

 

There are multiple reasons how this can happen and Whitetiger5 mentioned more data would be useful, Going uphill, downhill, driving speed, is just after acceleration, outside temperature, was the car warmed up when it occurred, was it idling , all these things can help narrow down the problem. Some are mechanical, a few like John from PA mentioned are purely electrical, as the vehicle is electromechanical more information is helpful.