After many attempts to find the solution to this problem of stalling, from changing coils to other attempts you may have tried yourself if you have a 3800 engine....here is our solution:
OK .... here it is short and sweet
The Phantom Stall:
Car in question is a 1994 Buick Regal, about 115,000 miles.
If you get a P1408, EGR fault Code on a 3800 Buick (et. al. 3800 engine)
Using a 12 vdc (polarity is not an issue) source (battery) operate the EGR, apply 12 vdc to #1 and #5 end wires on the connector, the middle 3 are the indicator wires they should read about 700 ohms in each direction. Using an Ohm meter check # 2 and #4 against the #3 toggling (middle wire) between valve open and valve closed (you can twist the #2 & #4 together to make it easier )
Applying 12 vdc to the outer wires (#1 & #5) check the ohm value on the #2 against #3 they should BOTH be near the same
within 200 ohms. If you get a high (over 1000 ohm) reading the computer won't recognize it, as was this Buick, the valve is working mechanically, but the ECU won't know what the position is? wrong readings?
My reading were 685 and 1800 ohms, no good.
Note that the check can be made in situ (on the car)
Hence the P1408 code
New the EGR is $160 usd
$ 12 USD at Ecology auto recycle, Bring your small battery and ohm meter and check each one (you can cut an old 5 wire connector off an old car and use it for the check and that makes checking the valve a snap, you may want to visit the yard first)
I looked at 3 EGR's and found one with 700 ohms in both positions installed it on the old Buick and the light stayed out.
P.S. you need to disconnect the battery for about 20 minutes to 'erase' the 'hard fault'
Car has been stall free and no engine light on for several days.