I have a 2002 Bonneville with the 3800 motor with around 150,000 miles and a couple of months ago it started to stall when idle. It will restart right away. The first mechanic said i have water in the fuel so he cleaned out the fuel system and the didnt work so then he the mechanic put in new plugs, wires, coils, Maf sensor, repaired a vacuum leak. It ran fine for about a week, now I have the same problem except it will cut on when driving in low speeds, which causes a problem because I lose all power, brakes and steering. Very scared to drive.

check engine light? codes?did they check the fuel pressure? what was it?

I haven't seen water in gas in a good 30 years, it just don't happen anymore.

Start by checking the fuel pressure. Should be around 48psi. If it'* less then that the engine can stall. You can change the filter, but generally these don't clog up real bad. You may have a bad fuel pump. A bit pricey, but easy to do, GM actually put a access door above the tank in the trunk.

I merged both your threads together.

There is no code and I am having the fuel pressure checked today. I will post with what I find out.
Thanks.

I would check the crank shaft position sensor. Fuel pressure issues, or a partially blocked fuel filter, are more likely to cause problems at higher speeds due to increased fuel flow. I've had cars with blocked fuel filters that would idle fine, and choke at higher speeds.

When the crank shaft position sensor failed on my car, it had the same symptoms you describe, except every once in a while it would not start. Leave it sit a bit, and it would start fine.

I agree the crank sensor could be the problem, but fuel pressure is way easier to check. When it stalls does it shut down like a switch was flipped? Or does it sputter a bit and then die?

it would not restart right away if it was the crank sensor

Don't know if I agree with that. Mine would stall on the highway, and restart right away. Several times it stalled and restarted on its own due to still being in drive and road speed turning the engine over.

It shuts off like a switch was flipped.

not saying it cant happen but the majority of the time its heat soak that makes the sensor fail as its going out and it would still be heat soaked after your engine dies.