Hi everyone, Got a 2002 SLE that can't drive anymore as it'* gotten too unreliable. Has the stall at idle issue that appears to be fairly common, and can be caused by LOTS of things. The forum has been great at helping learn about all the in'* and out'* of this GM.
The issue, stalls at low rpm, like coming to stop sign and now often--- starts and immediately stalls.
of course there are NO Codes, that would be too easy.

Car seems to run okay when at speed, which would appear to rule out exhaust issues.

There have been only two part replacements, the IAC valve, guess what, you pull it instead of push it and it comes apart .. didn't trust it after that so bought a new one. Also replaced the plugs, they were original and actually they all looked good for 109K miles, new ones made no difference to issue.

I have done the following checks per the advice and where available, procedures on the forum:
Checked fuel pressure, normal - pressure reg functioning ok
Checked all grounds and battery connections - car is amazingly clean I had the cabin down to metal in about an hour thanks to the forum data on removing things, connections looked good, re-did them anyway
TPS, smooth ramp, both on meter and watching with scan tool
MAF, cleaned, seems to respond ok on scanner
MAP and PCV, just inspected and cleaned pcv
EGR, inspected and cleaned, it looked good, no sticking or binding
checked coils and ICM per procedure, everything checked out, no cracks, resistance good
Cam magnet is there and is clean
checked wiring to/from Cam and Crank sensors, connections good
Checked wiring at ECM/PCM
checked all relays and fuses, and connections under rear seat reseated all grounds and battery connections
Checked connections at starter, no issues noted
Checked all wiring which ran across engine looking for any issues, none noted
Ran a bottle of Fuel Injector cleaner through, just the gas add in kind. so not a real good clean I know.
when looking at real time data on scantool:
vacume at idle is about 9.5 to 10"
timing advance starts at +7 at start and ends up at +22.5 after idling for a while (normal ?)
inlet air temp sits around 120 (at idle) which seems high to me as it'* 75 outside.
O2 sensor voltage seems to cycle like its is supposed to.

A new wrinkle is in the last few days of testing, sometimes when turn key to start, just sits there, long enough for fuel pump relay to kick off (so > 3 sec or so), then suddenly will crank and start, hasn't done that before, will still die most times so don't know if that is related to stall issue.

My next steps are taking to a shop with a full scanner in the hope they can see something I can't, and I have my fears on that, or starting a parts swap from the boneyard aka shotgunning it.

Unless somebody can think of something else to try.

Test the battery cables. Sometimes they can corrode inside causing problems.

Totally removed them (the cables) from the back, they hardly even have any copper oxide on them.. resistance minimal. So have moved on, since have fuel pressure, looking at control and air:
Removed throttle body, was a little gunked, and a faint hint of some coolant seepage at the bottom, but no evidence of coolant in intake manifold, a few sprays of throttle body cleaner and it was spotless.

I did pick up a coil and ICM pack from a yard, I will swap them out today and give it a go.

I fear the PCM but will eliminate everything else first. It'* so bad I'd have to have it towed to the shop for a diag check.. I'll play for a bit longer before I bite that one.

Would anyone happen to know how the PCM "KNOWS" where the throttle is based on the throttle position sensor ? my initial resistance is 1.34 which seems high.. tracks smoothly, but how does the PCM calibrate itself so it knows what voltage signifies zero throttle position? On to the TPS as the coil and ICM swap did not affect stall issue at all.

96 Bonneville SE

I'm having a similiar problem. My initial TPS ohm reading is 1.249 ohm. No idea if this is within specs.

Was thinking about this, I have disconnected just about every device at one time or another and either tried to run, or actually run the car.. TPS, MAP, MAF,EGR,EVAP Solenoid, and the car has NEVER thrown a code.. isn't that a bit odd..

I'm leaning towards the PCM...it'* really odd that your not throwing any codes. Are you checking DTC with a scanner or looking for the SES light in the dash? If it'* the SES light you are looking for, you might have a burned out bulb.

checking for codes with scanner.. never show'* any codes, even when I'm hooked up and it dies.. and all warning lights illuminate during startup.. I'm thinking I have intense in my future.

Did you try the MAF sensor. My car had issues where it would die at low RPM and that was the issue. There are many guides online to check to see if yours is working properly, and you can hook up the tech II and check as well.

On a TPS sensor the only good test is volts. You should see 0 at key on and nearly 5.00 at WOT.

As for the rest of this.. there are quite a few cases of a crank sensor causing this type of issue.

My personal feeling on the best route to diagnose would be check connections at pcm for clean and snug. Unplug the maf and see if the condition replicates. Look over the crank and cam sensor wiring for any nicks or dings. If you get through all this and can't find a code or reason, my first thing to swap is a crank sensor. After that, if the condition still exists then the pcm.