It could very well be the VATs. On that year I believe it will start the engine and then shut down the injectors right after. Try a different key. Here is a write up on how to bypass the VATs system. https://www.gmforum.com/electrical-133/bypass-vats-92-99-a-279119/

I think we need a review of suggestions & work done to center ourselves and not repeat possibilities. I have taken the day off the project to clear my head. I'm back, coffee in hand Let'* review...

1. The engine never doesn't start. It always fires up.
2. Changed the ICM, both 3X & 18X tests give a pulse showing both circuits from CPS are okay, same as before. Car still stalls.
3. There is no VAT on this car.
4. I bought a noid kit: pulse is good.
5. I bought a fuel pressure test kit, the pressure is textbook even when the car stalls. This includes the pump operation before and after stalling. The rail mounted vacuum operated pressure regulator variance is textbook. The filter was changed early on. I have ruled out Fuel (More reasons I have ruled out fuel below, read on...).
6. The engine always starts back up and runs strong on all 6. Sometimes it will fire off and stall while cranking, but it always fires. When this happens, I let go the key and start again, it runs from 1 second to 30 on average. There was 2 times lately it actually ran for 15 minutes. This is when I was testing the fuel. I had just cleaned the MAF sensor and started in on the fuel test. It ran strong, revving up and such. I shut it off and happily ate lunch. 30 minutes later I ran it a 2nd 15 minutes. Feeling all proud of myself, I went for a test drive. It went 4 houses down the street and shut down. The neighborhood drunks all cheered. That'* okay, they helped push it back up into my driveway...
7. Oh and I even put on a new fuel pump relay (the Bosh lookin thingy behind the headlight).

New information: I bought a used ICM ($5) and mounted it. The car ran without stalling! The running characteristics changed drastically giving me renewed hope. It ran on high idle for a minute but as it warmed I had to hold part throttle. As the engine warmed up, it started sputtering like an old carburetor running out of gas; i.e. Starving for fuel. It would get to the point that it would not idle and stall. It would start right back up; I had to keep it running with cracked throttle. Also as it warmed, it would loose power to rev up. Just like a starving engine. It wouldn't stall after a few minutes doing this, but my finger got tired of holding the throttle open and I'd just let it die. Sometimes it would sound like it was coughing and kicking backwards as it stopped turning.

I figured I had found the problem and just went and bought a new ICM. When I started the car I was back to the original 1-30 second stalling, but with full power and no sputtering; just back to the instant shut down. THIS IS GOOD NEWS; It tells me that the all the sensors are okay since the car just kept running! riiiiiiight?

AH HA!! It seems we have a problem with the ICM & ECU talking to each other. All the sensors have been changed. Now I have a change of running patterns that are related to the brains.

So I went and got a used Engine Control Module and changed it. When I started it, the car would not run when I let go of the key to the run position. It immediately stalled, time after time. Put the old one in; back to running a few seconds, then stalling.

Okay so then I opened the ECU to look inside. My father was a Class A Radio Operator back in the 50'* and a rather good electronics fella. I looked for things he taught me like burned parts, split capacitors and cold solder joints. This thing is bright and shiny, through and through... So is the other one I bought. Every part on the mother board is identical. The only difference is on the ROM. There are 2 parts I can see inside the plastic retainer. The Motorola number is the same, but the other part number is major different. I'm sure due to different factory computer config'*. The "other" ECU is out of a Olds Cutlass Ciera with a 3300. Same numbers on the paper labels. It all adds up.

Hmmmm. Looky here! this ROM chip pulls out like a memory stick on my PC. This gave me an idea! I switched the ROM'* and guess what. My car'* ROM runs the car the same way on the other used board! Switching the ROM cards, switched the running patterns. Me thinks the mother boards are okay but the ROM is bugging out.

Then it hits me! This "single mom" (remember this is my ex-sister-in-law) ran with a sulfated battery and she also drove her starter into the ground, starting it until she fried the windings and running the brushes into the metal mounting screws. The armature was a rainbow of colors & the varnish all fried away smelling like an electrical fire.

After the car running trouble free for almost a year after buying it, the starter and battery fries. It was shortly after that, that the stalling showed up. And yes I told her to bring me the car to rebuild the starter. Always "I don't have time". You know the drill. Some people don't listen.



Okay, so now I go to buy a new ECU and I find that they only sell the silver box with the mother board, They don't sell the ROM. Buick Service Dept. tells me it'* discontinued. I have search engined my self ½ to death. I know that harsh jolts and serge'* will change settings and fry, just like static can fry a circuit.

No one I talk to can tell me how to test the ROM memory stick off of ECU (which probably can't be done) and the car wont run long enough to put anything in the memory. I have had to disconnect the battery overnight and that is supposed to clear any memory.

So that'* where I'm at. The ICM and the ECU aren't talking. Something is triggering a shut down.

Q: How the heck do I find an aftermarket ROM or have this one tested and/or reprogrammed.

Another thing that comes to mind is a possible ground problem. There is a ground under the ICM, make sure it'* clean and tight. Check all grounds and hot connections. At the battery and on the block. You have a connection at the alternator, but I don't suspect that as causing a stall. The problem will be between the battery and block, or block to ICM. You have a battery cable ground, as well as a ground on the back of the block above the oil filter. If you have a loose connection, or corroded, it can have intermittent loss of ground causing a stall.

anyone that tunes 95 and earlier vehicles should have a programer

I didn't have much time today to deal with this. It was dip the Quadrajet day for my Park Avenue.

I will check the rear bonding strap tomorrow, rain permitting. I'm pretty old school and keep my connections clean, tight and protected. I wire brushed under the ICM because I found silicon there. It'* a clean connection. But I did forget about the bonding straps and this is an electronic engine...

I did a few minutes of searching. I found some information on hacking the codes in the ROM and reprogramming the cards. I am going to visit a dynotune shop near me and talk to them. This IS Los Angeles, there must be a Hot Rod shop around here somewhere lol. I also found flash drives you can send for with programs on them to 'flash' your chip. All too cool.

Tomorrow I have to put in some job apps. I'll get back to ya mid-week.

My mind just wouldn't let go of some of the test procedures I got from different people. Shops I talked to just didn't uinderstand why I was asking them if htey had GM experience and understood the GM bypass ECM system. I tried to understand WHY I was testing something, not just how. Growing up with an allen wrench in my pocket to adjust the dwell on my 1965 GTO has found me falling short over the years in the electronic engine department. I went forward with tests I came to the conclusion that some of items I replaced was a total waste of time.

Take the Crank Position Sensor... Since there is no Cam Sensor on the 3.1 or 3.3 V6, both the Fuel and the Spark signals come from the CKP. Since I had spark, There was no reason to suspect it for Fuel signal problems.

I still say there is a problem with the source for the ICM test in the GM forum Tech section. First of all, the test there test only the CKP. The tests for the 3X loop and the 18X loop are both supposed to show the the 0-6V pulse. So the suggestion that the 18X pulse means that the ICM is bad as not possible. A yes means that the CKP is working and has nothing to do with the ICM at all. This is a RETURN pulse from the CKP and is taken BEFORE the pulse gets back to the ICM. Please revise the outcome for that procedure. It'* wrong.

Please understand, educational materials are wrong 18% of the time! Federal statistics have shown that over and over. Especially when the engineers that develop this stuff, are not the ones publishing the books! I remember one points and condenser ignition chart in my tune-up class showed a image of the AC ground in the secondary stinger, grounding to the Negative terminal of the primary winding in the coil. It took an electrical student to go and tap the teacher on the shoulder and point out that AC grounds to positive and should be going to the Positive terminal of the primary winding in the artwork.

I did some hard thinking about the diagram in my service manual for the fuel injectors. I was really confused by what I saw. So I started in on the test procedures for the fuel injectors to try to learn why GM set it up the way they did. I still don't know! hahaha

What confused me was the diagram showed that the 6 injectors were split into 2 loops. One with pink & blue wires and the other 3 bank has pink & green wires (looking at the top of my engine I saw the two loops). Then the darnedest thing happens! The 2 loops go into the computer and tie together at the "injector control". I believe I saw this controller on a video as a transistor. This system does not fire the injectors sequentially, but in a batch! All 6 injectors fire at the same time! What the heck? I understand firing the plugs in a batch, but MPI'*??

Well let me move on...

Each injector should test at 12.6 ohms. I tested all 6 and came up with...

__________________________
(left side of car)

12.7 -- 0.8 <--- can all my friends out there say "Dead Short"?

10.7 -- 12.8

11.2 -- 12.5

(right side of car)

It looks like the injectors go into the intake ports... and they do!

But the open plenum still has enough fuel floating around in the open space that some fuel air mixture can backflow and go into other ports. Up till now the mild thumping I felt on one cylinder I attributed to a bad wire. Guess what? A dead injector is not going to cause a dead cylinder, just a week one. IF I had detected a dead cylinder 4 months ago, I would have changed the injector back then! Remember I said I changed 5 of the 6 injectors. The one I left looked okay, and was clean in the shoot, BUT it was an off brand aftermarket and thus made a fool out of me!

So I went to the pull it yourself junk yard yesterday and bought a used Rochester Products injector for $6. You bet I took my multi meter and tested injectors until I found one with 12.6 ohms flickering to 12.7. I passed up others with 10 or 11, or even 12.2. In the near future I will change the 10 & 11 ohm injectors so they are all up to par.

Here'* what happened. When the car pulled its first stall, it was up a hill under load. Then after a couple under load stalls, it just started stalling anywhere. The damage had set in.

(Here'* a story for if you are bored. If you're in a hurry, skip to the next paragraph) Well the last day it was on the road was a bear. It stalled 10 times in 5 miles. I had the owner of the Buick following me in my Mitsubishi to push me out of intersections if need be. I even got pulled over by LAPD because while it is legal to tow a car with a rope or chain, it'* apparently illegal to PUSH a car with another car. I handed him my CDL and told him I had pulled cars and read the Veh Code many times and was aware of laws saying things like you can't pull a car with a rope or chain over 10 feet long, and you can't tow a car off a state highway with a rope, it HAS to be a chain, but I've never heard of this law. He was quite agitated and looked like he was going to write me up. When I told him that the car was running under it'* own power until the last intersection when I motioned my friend to push me out of the intersection, he calmed down a tad. Then I pulled out my AAA card and said I would call a tow truck. He asked why I hadn't called. I said I live 6 long blocks from where the car first stalled (big lie, lol) and had been rescuing cars all my life even with police cars driving by me. He said to park it and get a tow truck and drove away *whew*! So I let the car cool 15 minutes and started it up and drove it *almost* home. She had to push me the last 100 yards. No disrespect to the kind officer!

So back to what happened...

When one injector shorts, it puts a such a load on the triggering transistor, AKA the injector controller, the controller overloads and just says "I Quit!" and shuts down ALL 6 INJECTORS.

Then you start it right back up, and overloads and stalls again.

So, if you ever hear of someone having instant "turning the key off" type stalling, remember that the fuel injectors and those wires are part of what has to be tested under the hood. Not just the sensors and ICM. If you don't it'* like testing 1/2 the car and ignoring the other 1/2. Ask your self this: "Would I check only 3 of the 5 lug nuts on each wheel to find the loose lug nut?"

Anywho...

I drove the car today on all my errands. I think I put about 35 miles on it. I also got a call from the owner to go pick her up from the hospital as her daughter had some GI tests run (maybe it was her injectors? lol)

I pulled in and drove towards them. They were looking past me for my big Park Avenue. It wasn't until I jerked the wheel and aimed right for them and goosed it, that they realized it was their Century lol. Kathy screamed "IT LIVES"! She'* such a movie buff All the way home she was crying and saying "I can't believe it'* running". I don't blame her, it'* been sitting in my driveway for over 4 months!

So ends the saga of the Century (pun intended)

thanks for the update and good info