GM Service Manual Online
For 1990-2009 cars only

Inspections

Action

DEFINITION: A jerking that follows engine speed, usually more pronounced as the engine load increases which is not normally felt above 1,500 RPM or 48 km/h (30 mph).

Preliminary

Refer to Symptoms - Engine Controls .

Ignition System

Inspect the spark plugs for the following conditions:

    • Insulation cracks
    • Wear
    • Improper gap
    • Burned electrodes
    • Heavy deposits
    • The ignition system for moisture, dust, cracks, burns, etc.

Engine Mechanical

    • Perform a cylinder compression check. Refer to Engine Compression Test in Engine Mechanical.
    • Inspect the engine for the following:
       - Improper valve timing
       - Worn rocker arms--Refer to Valve Rocker Arm and Valve Lash Adjuster Cleaning and Inspection in Engine Mechanical.
       - Worn camshaft lobes--Refer to Camshafts Cleaning and Inspection in Engine Mechanical.
       - Broken or weak valve springs--Refer to Upper Engine Noise, Regardless of Engine Speed in Engine Mechanical.
    • Inspect the intake and exhaust manifold passages for casting flash.

Fuel System

    • Test the fuel pressure. Refer to Fuel System Diagnosis .
    • Inspect for water contamination in the fuel. Refer to Alcohol/Contaminants-in-Fuel Diagnosis .
    • Perform the fuel injector coil test. Refer to Fuel Injector Diagnosis .