Stalling at low speeds and stops

Hi,

Have you confirmed there are no vacuum leaks at the intake even though it was replaced or anywhere? Also, was the idle air control valve replaced? Did you confirm that the fuel pressure regulator is working properly and the pressure is within spec? It should be between 50 and 60 psi.

https://www.2carpros.com/articles/stall-at-idle

https://www.2carpros.com/articles/how-to-check-fuel-system-pressure-and-regulator

Let me know.

Joe

Have you tried a throttle relearn? Take a look through these directions.

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2008 GMC Truck Yukon 2WD V8-5.3L
Throttle Learn
Vehicle Powertrain Management Fuel Delivery and Air Induction Idle Speed Testing and Inspection Programming and Relearning Throttle Learn
THROTTLE LEARN
Throttle Learn

Description

The engine control module (ECM) learns the airflow through the throttle body to ensure the correct idle. The learned airflow values are stored within the ECM. These values are learned to adjust for production variation and will continuously learn during the life of the vehicle to compensate for reduced airflow due to coking. Anytime the throttle body airflow rate changes, for example due to cleaning or replacing, the values must be relearned.

A vehicle that had a heavily coked throttle body that has been cleaned or replaced may take several drive cycles to learn out the coking. To accelerate the process, the scan tool has the ability to reset all learned values back to zero. A new ECM will also have values set to zero.

The idle may be unstable or a DTC may set if the learned values do not match the actual airflow.

Conditions for Running the Throttle Learn Procedure

With Scan Tool - Reset Procedure
* DTCs P0068, P0101, P0102, P0103, P0106, P0107, P0108, P0116, P0117, P0118, P0120, P0122, P0123, P0128, P0171, P0172, P0174, P0175, P0201, P0202, P0203, P0204, P0205, P0206, P0220, P0222, P0223, P0300, P0351, P0352, P0353, P0496, P0601, P0604, P0606, P060D, P0641, P0651, P1516, P2101, P2119, P2120, P2122, P2123, P2125, P2127, P2128, P2135, P2138, or P2176 is not set.
* Ignition ON, engine OFF.
* The vehicle speed sensor (VSS) is 0 km/h (0 mph).

Without Scan Tool - Learn Procedure
* DTCs P0068, P0101, P0102, P0103, P0106, P0107, P0108, P0116, P0117, P0118, P0120, P0122, P0123, P0128, P0171, P0172, P0174, P0175, P0201, P0202, P0203, P0204, P0205, P0206, P0220, P0222, P0223, P0300, P0351, P0352, P0353, P0496, P0601, P0604, P0606, P060D, P0641, P0651, P1516, P2101, P2119, P2120, P2122, P2123, P2125, P2127, P2128, P2135, P2138, or P2176 is not set.
* The engine speed is between 450-4,000 RPM.
* The manifold absolute pressure (MAP) is greater than 5 kPa.
* The mass air flow (MAF) is greater than 2 g/s.
* The ignition 1 voltage is greater than 10 volts.

Throttle Learn

With Scan Tool - Reset Procedure
1. Ignition ON, engine OFF, with a scan tool, perform the Idle Learn Reset in Module Setup.
2. Start the engine, monitor the TB Idle Airflow Compensation parameter. The TB Idle Airflow Compensation value should equal 0 percent and the engine should be idling at a normal idle speed.
3. Clear the DTCs and return to the diagnostic that referred you here.

Important: Do NOT perform this procedure if DTCs are set. Refer to Diagnostic Trouble Code (DTC) List - Vehicle. See: A L L Diagnostic Trouble Codes ( DTC ) > Diagnostic Trouble Code Descriptions

Without Scan Tool - Learn Procedure
1. Start and idle the engine in PARK for 3 minutes.
2. With a scan tool, monitor desired and actual RPM.
3. The ECM will start to learn the new idle cells and Desired RPM should start to decrease.
4. Ignition OFF for 60 seconds.
5. Start and idle the engine in PARK for 3 minutes.
6. After the 3 minute run time the engine should be idling normal.

Important: During the drive cycle the check engine light may come on with idle speed DTCs. If idle speed codes are set, clear codes so the ECM can continue to learn.

If the engine idle speed has not been learned the vehicle will need to be driven at speeds above 70 km/h (44 mph) with several decelerations and extended idles.

7. After the drive cycle, the engine should be idling normally.

If the engine idle speed has not been learned, turn OFF the ignition for 60 seconds and repeat step 6.

8. Once the engine speed has returned to normal, clear DTCs and return to the diagnostic that referred you here.

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The codes listed above may or may not be present.

Let me know.
Joe

In your first post, you identified throttle. Did you replace the entire throttle body? Also, I did some research and the only thing I can find related to an idle issue and no start is a carbon issue that was indicated in a technical service bulletin. Take a look at the pic attached.

Joe