If your LS engine hangs at higher RPM when you let off the throttle, the problem is usually not random. A few common tune or setup issues can make the RPM fall too slowly instead of returning cleanly to idle.

1. Throttle follower / cracker airflow is too high

These settings add airflow when you come off the throttle to help prevent stalling. If they are too aggressive, the engine can “hang” instead of dropping back down like it should.

2. Base idle airflow is too high

If the engine is getting too much airflow at closed throttle, RPM can stay elevated on decel and take too long to settle. This is common on LS swaps and cammed combinations if idle airflow has not been dialed in correctly.

3. Vacuum leaks or incorrect fueling data

A vacuum leak, incorrect VE or MAF calibration, or injector data that is off can all affect how the engine behaves when the throttle closes. Extra unmetered air or fueling errors can make decel feel unstable and keep RPM higher than expected.

Also check the basics

Before chasing tune changes, make sure:

  • The throttle blade is closing fully
  • TPS is reading correctly
  • There are no vacuum leaks
  • Idle airflow settings are reasonable
  • Follower / cracker settings are not excessive

A hanging RPM issue is usually a combination of airflow control, decel settings, and overall calibration.

If your LS swap hangs RPM on decel, send me your combo and current symptoms.

Midgard Industries EFI Tuning
Longview, Texas
midgardind.com

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