2024 ACDelco Tech Challenge - April 2024

Last month we asked this Tech question and invited you to share your answer. We value your expertise and want to thank everyone who participated!

When diagnosing a fuel metering to lean bank 1 code P0171, you notice the Short Term Fuel Trim moves from +10% to +2% when you bring the RPM up to 2500 from idle. What is the most likely cause of the lean condition?
The most likely cause is a vacuum leak. When you increase the RPM there is less vacuum and therefore less un-metered air entering the engine from the leak point. You will see the fuel trim move closer to zero, as the ECM reduces its rich correction for the lean condition. Your next step should be to perform a volumetric efficiency test to ensure the mechanical components are operating above 80% VE. Then use a smoke machine to find the cause of the intake air leak.

Congratulations to the following shops who answered this question correctly and will be receiving a prize pack!
  • Brock at Cox's Auto Clinic Ltd in Dartmouth, NS
  • Rick at Torque Performance Ltd in Edmonton, AB

The Tech Challenge question is published in our weekly eNewsletter with an online answer form. Fill out the form with the details of how you would perform the repair to be entered for the chance to win the prize pack. You can also submit a challenge for future Tech Challenges! A draw is conducted with all shops who answered the question correctly and one is selected as a winner for a prize pack.
Got a Tech Tip you want to share for a future Tech Challenge?  >>CLICK HERE to fill out our question form.
Watch for our next Tech Challenge question in our eNewsletter. Visit our blog page for more Tech Tips