Engine racing after cleaning throttle body

DALE PROVANCE

MEMBER
2012 CHEVROLET SILVERADO
5.3L
V8
2WD
195,000 MILES

I’ve been having trouble with the engine stalling so I cleaned the throttle body. It was filthy. I actually removed the four bolts and unplugged the harness so I could clean it very good. After putting all back together, it’s revving up like I’m getting ready to drag race. Staying around 3,000 rpm. I took the battery cables off to try and reset the computer and it seems like it’s trying to correct itself but not really. Please advise and thanks in advance.
Dale

1 Reply

JACOBANDNICKOLAS

MECHANIC
109,755 POSTS

Hi and thanks for using 2CarPros.

There is a relearn process that I will attache here. However, make sure there are no vacuum leaks at the induction tube or at the throttle body. Next, make sure the throttle body is fully closing. If it is, remove the idle air control valve and inspect it for debris.

The relearn is for multiple scenarios..
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Throttle Learn

Throttle/Idle 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 throttle body coking. Anytime the throttle body airflow rate changes, for example due to cleaning or replacing, the values must be relearned.

An engine 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

Reset Procedure

* 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 voltage is greater than 10 volts.

Throttle Learn

Reset Procedure (Performed after the throttle body is cleaned or replaced)
1. Ignition ON, engine OFF, perform the Idle Learn Reset in Module Setup with a scan tool.
2. Start the engine and 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.

Learn Procedure (Performed after the ECM is flashed or replaced)

Note: 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 > Diagnostic Trouble Code (DTC) List - Vehicle.

1. Start and idle the engine for 3 minutes.
2. With a scan tool, monitor the Desired Idle Speed and the actual Engine Speed.
3. The ECM will start to learn the new idle cells and Desired Idle Speed should start to decrease.
4. Ignition OFF for 60 seconds.
5. Start and idle the engine for 3 minutes.
6. After the 3 minute run time the engine should be idling normal.

Note: 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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Here are the actual directions for cleaning the throttle body.

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THROTTLE BODY CLEANING
Throttle Body Cleaning

1. Remove the air cleaner outlet duct. Refer to Air Cleaner Resonator Outlet Duct Replacement See: Air Cleaner Fresh Air Duct/Hose > Removal and Replacement > Air Cleaner Resonator Outlet Duct Replacement.

Warning

Turn OFF the ignition before inserting fingers into the throttle bore. Unexpected movement of the throttle blade could cause personal injury.

Caution: Do not insert any tools into the throttle body bore in order to avoid damage to the throttle valve plate.

2. Inspect the throttle body bore and the throttle plate for deposits. You will need to open the throttle plate in order to inspect all surfaces.
Caution: Do not use any solvent that contains Methyl Ethyl Ketone (MEK). This solvent may damage fuel system components.

3. Clean the throttle body bore and the throttle plate using a clean shop towel with GM Top Engine Cleaner, P/N 1052626, or AC-Delco Carburetor Tune-Up Conditioner, P/N X66-P, or an equivalent product.
4. Install the air cleaner outlet duct. Refer to Air Cleaner Resonator Outlet Duct Replacement See: Air Cleaner Fresh Air Duct/Hose > Removal and Replacement > Air Cleaner Resonator Outlet Duct Replacement.
5. Perform the Throttle Learn Procedure. Refer to Throttle/Idle Learn See: Idle Speed > Programming and Relearning > Throttle Learn.
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Let me know if this helps or if you have other questions.

Take care,
Joe