Engine shut off

[skivolks]

I have a 92 k2500. The engine shuts off randomly while driving every few months. The power does not shut off when this happens. I always restarts after turning the key off then starting again. Any ideas about how to fix this? 350 tbi engine, all stock

 

[Road Trip]

I have a 92 k2500. The engine shuts off randomly while driving every few months. The power does not shut off when this happens. I always restarts after turning the key off then starting again. Any ideas about how to fix this? 350 tbi engine, all stock

Greetings skivolks,

Welcome to the GMT400 forum! In order for the remote troubleshooters to get a better
feel for your situation, could you please answer the following questions?

* While you have owned it, did the truck ever run without doing this to you? (For example,
let's say that you owned it for 5 years, and the first 4 years it never did it?) Or, has the
truck done this intermittent shutdown the whole time you have owned it?

* Is the ignition switch original? Do you have 2 keys or 20+ keys on your ring?

* Is the computer currently throwing any codes? Has it ever thrown codes? Or does the SES light
come & go over several trips?

* How old are the usual tune up parts? And the distributor. Original? Newer OEM? Or aftermarket
replacement?

* Can you list all the times that it has never shut off? For example, never fails cold. Or has never
failed before running ~30 minutes. Never fails in the winter, but the failures increase at the temps rise?

* Has the Idle Air Controller ever been cleaned? For that matter, how many miles are on this engine?

* Does the failure only occur during a closed throttle decel right before a stop, or will it suddenly
cut out during a steady cruise down the highway?

* Have you experienced any other electrical intermittent problems coincident with the engine shutting off?

* Have you ever been able to check the fuel pressure when this occurs? (Thinking fuel pump as victim
of losing electrical power?)

* Anything else about the truck that you would tell me about right before I borrowed it? These old
gals tend to have some personality, and there could a clue hidden in there if you know what I mean. :0)

****

I'm trying to cover the basics. Things like a sticky IAC, thermal sensitive ICM in tired dizzy intermittently
dropping the 'Reference' signal to the computer when the going gets hot, ignition switch worn out, etc.
In other words, a random intermittent connection will present in one way, while a thermal intermittent
will have a different failure footprint.

We're sitting around a virtual campfire, so feel free to tell us as many details as you can remember. The
thing is that 30+ year old trucks have many different ways of confounding us with their shenanigans, and
in here none of us favor the use of a parts cannon. The good news is that there is a *lot* of experience
in the audience, and if you identify a quirky behavior that someone in here has also experienced/fixed, then
we may be able to sort this out in the fewest possible attempts.

Note: If we can figure out how to break this at will, then if we can be collecting live data when it happens
we will have a much more precise idea of what's going wrong.

Get back to us with the answers to the questions above, and we'll start kicking around the possibilities.

 

[Schurkey]

The Usual Three:

1. Verify fuel pressure at prime, at idle, and under load. Most fuel pressure gauge assemblies have a push-button pressure release connected to crappy vinyl tubing. Route the tubing so it empties into a drain pan, then push the button while the engine is running. This simulates higher fuel demand if you can't check fuel pressure on the highway. Fuel pressure should remain steady even with fuel flowing down the pressure-relief tubing. How old is the fuel filter? Have you ever dumped a bottle of Chevron Techron Complete Fuel System Cleaner into the gas tank? (Recommended at every oil change.)
   
2. How old are the usual “tune-up” parts and procedures? Inspect/replace distributor cap, rotor, plug wires, spark plugs. Make sure the ignition coil will reliably fire a spark-tester calibrated for HEI when the coil is fully warm, and misted with water from a squirt-bottle. Cranking compression test of all cylinders while the spark plugs are removed. Verify EGR, PCV, EVAP, and Heated Air Intake (if used) systems for proper operation. Verify proper initial timing (TBI) and electronic spark advance (TBI and Vortec). Replace old O2 sensors unless you can PROVE that they're working properly—old O2 sensors get lazy, they don't provide accurate data, but they do provide “data” that fools people into thinking they're “working”.
   
3. Connect a scan tool (NOT a crappy “code reader”) and look for “codes”. More important, look at the data stream to verify EVERY sensor and computer output. Verify fuel trims during the time that the vehicle is not running properly. Look for misfire counts for each cylinder (OBD2 only.) “Codes” have official diagnostic procedures that will be found in the service manual set for your vehicle. The service manual set can be downloaded from the links in the Sticky thread section of the Engine forum on this web site.

 

[skivolks]

Greetings skivolks,

Welcome to the GMT400 forum! In order for the remote troubleshooters to get a better
feel for your situation, could you please answer the following questions?

* While you have owned it, did the truck ever run without doing this to you? (For example,
let's say that you owned it for 5 years, and the first 4 years it never did it?) Or, has the
truck done this intermittent shutdown the whole time you have owned it?

* Is the ignition switch original? Do you have 2 keys or 20+ keys on your ring?

* Is the computer currently throwing any codes? Has it ever thrown codes? Or does the SES light
come & go over several trips?

* How old are the usual tune up parts? And the distributor. Original? Newer OEM? Or aftermarket
replacement?

* Can you list all the times that it has never shut off? For example, never fails cold. Or has never
failed before running ~30 minutes. Never fails in the winter, but the failures increase at the temps rise?

* Has the Idle Air Controller ever been cleaned? For that matter, how many miles are on this engine?

* Does the failure only occur during a closed throttle decel right before a stop, or will it suddenly
cut out during a steady cruise down the highway?

* Have you experienced any other electrical intermittent problems coincident with the engine shutting off?

* Have you ever been able to check the fuel pressure when this occurs? (Thinking fuel pump as victim
of losing electrical power?)

* Anything else about the truck that you would tell me about right before I borrowed it? These old
gals tend to have some personality, and there could a clue hidden in there if you know what I mean. :0)

****

I'm trying to cover the basics. Things like a sticky IAC, thermal sensitive ICM in tired dizzy intermittently
dropping the 'Reference' signal to the computer when the going gets hot, ignition switch worn out, etc.
In other words, a random intermittent connection will present in one way, while a thermal intermittent
will have a different failure footprint.

We're sitting around a virtual campfire, so feel free to tell us as many details as you can remember. The
thing is that 30+ year old trucks have many different ways of confounding us with their shenanigans, and
in here none of us favor the use of a parts cannon. The good news is that there is a *lot* of experience
in the audience, and if you identify a quirky behavior that someone in here has also experienced/fixed, then
we may be able to sort this out in the fewest possible attempts.

Note: If we can figure out how to break this at will, then if we can be collecting live data when it happens
we will have a much more precise idea of what's going wrong.

Get back to us with the answers to the questions above, and we'll start kicking around the possibilities.

Thanks, I may have fixed the problem.. bad lock cylinder. Time will tell, it's not for sure

 

[Road Trip]

Thanks, I may have fixed the problem.. bad lock cylinder. Time will tell, it's not for sure

I appreciate the status update.

With a tough intermittent like this, if you have an idea about the original failure interval
(once every other day, or once a week while commuting to work, once a month,
etc) ...then the rule of thumb we used to use on the flightline was to wait twice the
original failure interval before declaring a fix.

And if the problem returns, then we simply continue with the Process of Elimination.
Taking sniper shots driven by a failure theory is not the same as filling the parts
cannon and shooting indiscriminately. Unless we have o-scopes and a shop full of
test gear sometimes we have to change a part, wait twice the failure interval, and
see what happens.

Looking forward to your next status update. No time pressure. Fingers crossed
that it's the twice the failure interval, all is well message.

Safe travels --