Possible Causes & Corrections
WARNING: This page is about a different car, the 2003 GMC Sierra, 2003 GMC Cab & Chassis Sierra, 2003 Chevrolet Silverado, and 2003 Chevrolet Cab & Chassis Silverado. However, it is still accessible from the selected car via links, so may be relevant.
Check the following items:
- Compare scan tool data at idle with scan tool data list. See PIN VOLTAGE CHARTS - SILVERADO & SIERRA article.
- Observe Fuel Rail Pressure (FRP) sensor and fuel pressure regulator commanded percent at idle. FRP should be near 40 MPa, and commanded percent should be near 40 percent. If command is high, a fuel pressure or sensor problem exists.
- Inspect for an intermittent Crankshaft Position (CKP) sensor signal.
- Inspect CKP sensor reluctor wheel. Remove 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.
- Perform engine compression test. See CYLINDER COMPRESSION PRESSURE under MECHANICAL INSPECTION under PRELIMINARY INSPECTION & ADJUSTMENTS in BASIC DIAGNOSTIC PROCEDURES - 6.6L SIERRA & SILVERADO - DIESEL article.
- Inspect engine for improper valve timing, bent push rods, worn rocker arms, worn camshaft lobes, or broken or weak valve springs.
- Inspect intake and exhaust manifold passages for casting flash.
- Inspect for plugged fuel filter, high vacuum, air in fuel system, etc.
- Inspect for water contamination in fuel.
- Inspect fuel injectors for proper operation. Perform Fuel Injector Balance Test using a Tech 2 scan tool.