Diagnostic Aids
WARNING: This page is about a different car, the 2019 GMC Savana 3500, 2019 GMC Savana 2500, 2019 Chevrolet Express 3500, and 2019 Chevrolet Express 2500. However, it is still accessible from the selected car via links, so may be relevant.
Possible Causes of an Engine Overspeed
- Aftermarket power-up devices
- Leaking or failed turbocharger oil seals
- Oil evident in the intake runners and compressor side of the turbocharger
- Starting fluid use or alternative fuel added to the engine such as ether
- Excessive oil build-up in the charge air cooler