Section 12 (Engine Controls - 6.6L - Troubleshooting & Diagnosis): Surges/Chuggles

WARNING: This page is about a different variant/trim than selected.

Surges/Chuggles

Inspection	Action
DEFINITION: The engine has a power variation under a steady throttle or cruise. The vehicle seems to speed up and slow down with no change in the accelerator pedal.
Preliminary Inspection	Refer to Symptoms - Engine Controls . Ensure the driver understands the torque converter clutch (TCC) operation. Ensure the driver understands the A/C compressor operation. Compare the scan tool data at idle with the scan tool data list. Refer to Scan Tool Data List (Engine Control Module) or Scan Tool Data List (Glow Plug Control Module) . Use the scan tool to ensure the vehicle speed sensor (VSS) reading matches the speedometer. This excludes vehicles with electronic transmissions where some variation between VSS and the speedometer is normal.
Sensor Inspection	Turn ON the ignition with the engine OFF. Observe the actual fuel rail pressure with a scan tool. The actual fuel rail pressure should be between 1.1-1.8 MPa. If it is not, inspect for high resistance in the fuel rail pressure (FRP) sensor circuits or the FRP sensor. Refer to Circuit Testing and Wiring Repairs . Test for an intermittent FRP sensor signal by wiggling the harness between the sensor and the engine control module (ECM) with the ignition ON and the engine OFF, while monitoring the parameter with a scan tool. Observe the FRP sensor and the fuel pressure regulator commanded percent at idle. FRP should be near 40 MPa, and commanded percent should be near 40 percent. If the command is high, a fuel pressure or sensor issues exists. Inspect the crankshaft position (CKP) sensor reluctor wheel. Remove the CKP sensor and attempt to move the reluctor wheel front to back or side to side with a probe. If there is any movement the reluctor wheel retaining bolts are loose.
Fuel System Inspection	Inspect the fuel supply system vacuum while the problem exists. Refer to Fuel System Diagnosis . If the ECM glow plug control module (GPCM) or a fuel injector has recently been replaced, it may be necessary to confirm the fuel injector flow rate values. Refer to Fuel Injector Flow Rate Programming . Inspect for a sticking Fuel Pressure Regulator. The symptom for this condition will be an idle surge of at least 100 RPM. This surge will be from 50 RPM above Desired Idle Speed to 50 RPM below Desired Idle Speed. Refer to Fuel Pressure Regulator Diagnosis .
Additional Inspection	Inspect the control module grounds for being clean, tight, and in their proper locations. Inspect the generator output voltage. Repair if less than 9 volts or more than 16 volts. Inspect the TCC operation.