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Discussion Starter #1
Hello All,

Need your assistance to track down a frustrating intermittent problem.

Background
1996 SS with 107K km (66K mi). Purchased the car about 2 years ago with 85K km (50K mi) and immediately replaced the plugs, all filters (incl fuel), all fluids, hoses, added at least 4 cans of fuel injector cleaner, etc. Engine management computer had no stored codes when I bought the car or since. The car is not winter driven and only on the road when temperatures are above ~15C (~60F). I drive it at least once a month to keep it healthy. The exception is the ~4 winter months when it is on a trickle charger but I do start it regularly and drive it around the yard.

Issue
Over the past 18 months the car inexplicably stalled twice immediately after starting the car, putting it in gear and pushing the throttle. Until yesterday - then it did it 5 times, twice when first started (cold engine) and three times with the engine at operating temperature (71C / 160F thermostat). In 4 of the cases it was immediately after pushing the throttle coming off idle. The fifth time it was while travelling very slowly through a parking lot about 15 seconds after 2 stalls immediately after starting the car (stopped for ~5 minutes for a coffee). The fifth time was similar in that it happened as I touched the throttle the only difference being I was moving. At no time did the Check Engine light come on or any other warning light.

What is also unusual about some of these events is the reset of the clock on the stereo. It doesn't happen every time it stalls, maybe 2 out of the total of 7 events. The fact that the clock resets to 1:00 leads me to believe a complete electrical cut out - similar to disconnecting and reconnecting the battery.

I should also point out I swapped the battery with a known good one a few month ago. The first two events occurred with the previous battery and the 5 yesterday with the replacement (not new but less than 5 years old).

After the 'stalling events' I drove the car to the airport and back (~300 km / ~185 mi - 90% highway), over a 6 hour period (a few stops in between). NO ISSUES during the entire trip. Halfway through the trip I stopped at my son's place and borrowed his OBD II tester - no codes logged.

It must be electrical related. I assumed a bad ground or loose connector but that wouldn't explain the reset of the stereo clock. One possibility is an electrical spike coming from the alternator that is tripping a surge suppressor or over voltage circuit (assuming these cars have one or both of these), causing the +12V feed to momentarily cut out? I have tested the alternator output to the battery and it is the normal 13.5 - 13.8V with the headlights on - bear in mind that this test was not done after one of the stalling events.

So .... I'm puzzled / stumped / frustrated!

I await your learned insight and feedback.
 

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with no codes the fuel pump circuit should be checked ..

in the trunk the wiring goes to the fuel pump and the ground is in the trunk at the driver side hinge..disconnect the trunk connector for any damage.. measure the volts going to fuel pump... the other connector is behind the rear license plate..

fuel pump relay is in the under hood fuse box .. remove the plastic cover check out the contacts if pitted replace .. also the relay socket pins ..

on the radio clock in the cold weather over the last few years the clock does go off ..

my 1996 SS is running perfectly .. 84K miles.
I do install gas stabilizer 100% of the time .also 2 OZ of MMO when I get gas..
 

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Some of my personal experiences

In my next post, I'll try to address your issues more specifically.

This one time, my girlfriend and I were being recreationally affectionate, and she was so ravenous, next thing I know, I … um … finished too soon …

So I checked my fuel pressure the next morning. Good thing I did, fuel pump was just beginning to falter. Ordered one that day, installed it about a month later, when symptoms became more obvious in daily driving.

Moral: Whenever ANYTHING goes wrong, it's never a bad idea to check fuel pressure. Seriously. (Actually happened.)

… ANYWAY …​
Many moons ago, with the wagon in my sig, I and one of my best driving students started noticing that the engine would either stutter, stumble, or stall if the steering wheel was turned to the right (not left) while braking during the entries for right turns.
No matter what, engine always behaved perfectly if the turn came after a stopsign or redlight-turned-green.
She learned to get around it by finishing with the braking earlier, and then putting her foot on the gas GENTLY, BEFORE steering into the turn.

After the lesson was over, I opened the bonnet and started gently manipulating the main engine harness. I could stumble or even shut off the engine by moving the harness about 3/4" from it's normal resting spot to the left.
Since I could not afford the best solution at the time, I instead applied at least 10 zipties to the harness so it would prevent that specific movement.
It worked … unless I was braking REALLY REALLY HARD while steering into a right turn.
For the last few years of my wagon's life, it just would not tolerate or allow enthusiastic trailbraking into right turns.

Anyway, the moral of that story is, go see if wiggling some wires and wire bundles duplicates the problem. It's FREE!
 

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Fresh Air Inspector,

When you turn the car on, instead of quickly turning the key from 'OFF' past 'Run' to 'Starter', try turning the key from 'OFF' to 'Run' and leaving it in 'Run' for 3 secs, TWICE, before actually starting the car normally.
If it still stalls, it's probably the fuel pump. If not, I think it's the fuel pressure regulator.

For reasons I can't fully explain but were nonetheless inspired by your words, I'm also suspicious of a switch in your brake pedal, the Throttle Position Sensor, the Idle Air Control Motor, or the wires between the alternator and the pcm, or the wires between the alternator and the coil, or the wires between the alternator and the Coil Driver Module.

Since this is an intermittent problem, the wiring between two components may be more likely than either of the normally likely components in question.

One other thing: is your AIRpump disabled and properly segregated from the intake?

I truly hope this helps.
 

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.... At no time did the Check Engine light come on or any other warning light.
This was the most telling when I skimmed yesterday.

....
It must be electrical related.

Not my read.



I assumed a bad ground or loose connector but that wouldn't explain the reset of the stereo clock. One possibility is an electrical spike coming from the alternator that is tripping a surge suppressor or over voltage circuit (assuming these cars have one or both of these), causing the +12V feed to momentarily cut out? .....

Sounds complicated. Considering your VOM readings I knee-jerked to FP/FPR/harness/pump and really with J-Cat on this one.

So .... I'm puzzled / stumped / frustrated!
Do the testing it takes to line out the fuel component. And the "cold stall putting in gear" I'd look into TPS, IAC, MAF..... And IC / ICM are maint. items after 25 years. Jus sayin.


I await your learned insight and feedback.

Go somewhere else for learned. All I got is 50 years of dum luck stalking and murdering GM gremlins. This forum (guys and search both) has really helped my kill rate.


Marky - not entirely sure I correctly read your preamble, but I really really enjoyed it.



EDIT: = you beat me to several same items. Evil minds think alike eh.
 

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Make sure connections are tight at the battery because it does
sound like a loose connection.
Also check and clean:

*Both battery terminals
*Battery ground at the engine which is right between the alternator and waterpump.
*short battery ground on pass side fender near battery
* B+ connection on stud at underhood fuse box.

Nab
 

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Make sure connections are tight at the battery because it does
sound like a loose connection.
Also check and clean:

*Both battery terminals
*Battery ground at the engine which is right between the alternator and waterpump.
*short battery ground on pass side fender near battery
* B+ connection on stud at underhood fuse box.
NAB


I believe Fresh Air inspector replaced his body mounts last year. This would suggest to me NAB's recommendations are the place to start.


If the clock reset is related to the engine shutting down a fuel pressure check will rule out pressure as a problem but you can not blame a fuel pump if it is not getting electrical power.


If the clock is resetting due to a marginal battery delivering low voltage on restart, a check for disturbed vacuum lines would be the place to start.
 

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96 Black, and to whom else it may concern,

You [all] probably read it correctly.
The morning after, I felt an out-of-the-blue, oddly persistent urge to check my fuel pressure.
Maybe it occured to me that, while she might forgive me for a boyish performance …[thankfully followed by a boyish recovery which probably earned me forgiveness]
She probably would NOT forgive me for stranding her somewhere with a dead car. Nor would I forgive myself.
 

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Discussion Starter #9
Hello All,

I'm overwhelmed with all the responses (and humour), highlights the value of this forum.

Tomorrow (Thu), I will start the troubleshooting process based on your feedback. It may be a few days before I can provide an update.

Once again, many thanks for all the input.
 

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your in Nova Scotia ? IMO put in the 180F T stat... engine must run above 170F..

PCM will not manage the fuel properly with low engine temps .. when the cold weather hits .. I up in new england is why I did not install the 160F T stat..

I do drive my 96SS in winter when the roads are clean and dry ...
 

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Discussion Starter #11
Hello All,

Once again, thanks for the feedback.

Yesterday (Thu) I did the following;
1. cleaned/tightened the battery terminals.
2. cleaned/tightened the battery to passenger fender ground and the engine ground (by the alternator bracket).
3. checked the +12V stud to the under hood fuse/relay panel (passenger inner fender). It was too tight to remove and re-seat, I was afraid it would break the plastic housing. :)
4. unplugged/re-seated the relays in the under hood fuse/relay panel.
5. unplugged/re-seated all the engine electrical connections (except the injectors).
6. cleaned/tightened the fuel pump ground in the truck (beside driver's side hinge).
7. unplugged/re-seated the fuel pump connector (behind the rear bumper, below the license plate).

It is too early to tell if one or more of the above have solved the intermittent stalling problem. Fingers crossed.

Z09B4U - good memory regarding my replacing the body mount bushings - I'm impressed. :) I did all the suspension bushings too - everything is the black (graphite impregnated) Energy Suspension items.

j cat - interesting logic. I prefer my vehicles to run a little cooler as opposed to the 88C (190F) that most new cars specify. I store the car in the winter and it is only driven a few kilometers every few weeks to keep things lubricated. It is too risky to drive a car during a Nova Scotia winter. They salt the roads and will even spray a brine solution prior to an expected snow fall. When you do have a sunny day the roads are often white from salt powder - it actually kicks up white dust when you drive around. Terrible stuff if you take pride in your vehicles.
 

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I have been to Halifax a few times .. it is a salty place lots of atlantic moisture so sure can be electrical connections / fuse sockets etc...

what I did when I buy new vehicles I put some dielectric grease in the exterior connectors .. reason is most all my vehicles I keep are 10 or more years old . I still have my 1984 camaro .. electricals on that all perfect but it needs a paint job...
GM paint peel in that decade ..
 
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