Stalling When Pulling Away From a Stop

[Machlen]

First-time OBS owner here... I have a 93 K1500 with the 5.7L V8. I have only had the truck for a few days and have experienced what seems to be an intermittent stalling issue. Some days the truck runs flawlessly, but other days this occurs:

I am cruising along anywhere from 35 to 55mph and then slow to a stop for a stop light/sign. I can sit at the stop light for as long as needed and the truck idles fine, does not sound too high or low and is a very smooth idle. However, when I lift my foot off of the brake and begin to press the accelerator, the truck dies. It happens very quickly and without any sputter, like all power is completely cut.

To have to shift into N or P and restart the truck with the accelerator depressed to get it to "clear up" and shift successfully back into D without stalling again. If I attempt to restart the truck without the accelerator depressed immediately after it "dies" in the explained scenario, it will not start. (Under normal circumstances it starts fine w/o the accelerator pressed, it only requires the accelerator to start when trying to start back up immediately after dying...)

Any/all suggestions are welcome and thank you all in advance!

 

[L31MaxExpress]

EGR opening too soon would be my suspect.

 

[movietvet]

What @L31MaxExpress said and/or check the IAC motor and make sure it is not gummed up at the pintle shaft and that the passage way and pintle are clean. Check for any vacuum leaks. Age of tune related components?

 

[docstoy]

What about vacuum ck valve at brake booster ?

 

[Machlen]

What about vacuum ck valve at brake booster ?

I saw some similar threads on here with brake booster vacuum lines being suspected... I pulled the vacuum line off the booster and plugged it off with duck tape to try and rule this out. Problem still persists even without the brake booster hooked up at all...

 

[docstoy]

So do you have a scanner ? So if when this occurs and all you have done is removing foot off of brake pedal without touching gas pedal then is it possible you are getting a voltage spike from stop lamp switch ?

 

[Schurkey]

What @L31MaxExpress said and/or check the IAC motor and make sure it is not gummed up at the pintle shaft and that the passage way and pintle are clean. Check for any vacuum leaks. Age of tune related components?

The Usual Three:

1. Verify fuel pressure at prime, at idle, and under load. Make sure the fuel filter is not plugging. New-to-you vehicle? Might as well replace the fuel filter, along with ALL the other fluids and filters except for A/C refrigerant/desiccant IF the A/C actually works.

2. Assure all "tune-up" parts and procedures are in good usable condition. Distributor cap, rotor, plug wires, spark plugs, PCV system, EGR system, EVAP system. Check initial spark timing, electronic spark advance, verify cranking compression, and look at the heated-air intake. Replace the O2 sensor. Avoid cheap-junk parts from Amazon and others with brand-names that look like a bunch of letters strung together at random.

Buying from a local parts store is more-likely to get you parts that AREN'T counterfeit.

3. Connect a scan tool, verify EVERY sensor, and computer output including IAC. Check fuel trims just before, and as the engine stalls.

 

[Machlen]

Going to replace IAC valve and fuel filter tonight/tomorrow and will report back. Any additional suggestions are welcome.

 

[Schurkey]

Going to replace IAC valve and fuel filter tonight/tomorrow and will report back. Any additional suggestions are welcome.

Stop replacing parts, start doing some diagnosis.

 

[Machlen]

Update: installed the new IAC valve and that did not resolve the issue. However, it does seem like the issue worsens when the truck is warm. For example, when coming to a stop after exiting the highway.

Stop replacing parts, start doing some diagnosis.

This is my next step… I borrowed a basic GM OBD1 reader from a buddy of mine. Will plug it in tomorrow and see if any useful codes come out of it.