Poor Engine Performance in High Ambient Temperatures

Some 2016-2020 Express and Savana vans equipped with the 6.0L V8 engine (RPO L96, LC8) may have a lack of power when driving up grades or after the vehicle has been idling for long periods of time in high ambient temperatures (90°F, 32°C, or above). The poor performance may be more noticeable when the vehicle is outfitted with heavy work equipment, such as work boxes or ambulance bodies. When the ambient temperature drops below 90°F (32°C)°, the condition is less noticeable or is eliminated altogether.

The poor engine performance may be due to the high ambient temperatures affecting the intake airflow to the engine. The GDS 2 scan tool data will show an increase in total knock retard and backed out ignition timing, both of which may occur when the vehicle is under load or driving up a grade and more throttle input is required. The Engine Control Module (ECM) is adjusting to protect the engine from damaging spark knock, which is a normal operation under these conditions.

If poor engine performance is noticed, there are a number of components to check to determine if they are installed correctly or not missing or damaged. Any missing or damaged components could allow hot air into the intake duct, resulting in a lack of power. For example, check the intake duct for any restrictions, proper installation and any missing clamps. (Fig. 22)


Fig. 22


Other components to inspect include the hood seal, radiator baffle, air box, and exhaust system as well as any modified components. Refer to #PIP5800 for a complete list of components that should be inspected if the lack of performance condition is present.


– Thanks to Richard Renshaw

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