Chevrolet Silverado / GMC Sierra. Service manual — part 1221

ENGINES

Dirt or chips in valve lifters

Remove lifters and

remove dirt/chips

Excessive valve lifter leak-down

Replace valve lifters, See

ENGINES

Valve lifter face worn

Replace valve lifters, See

ENGINES

Broken or cocked valve springs

Replace or reposition

springs

Too much valve stem-to-guide clearance

Replace valve guides, See

ENGINES

Valve bent

Replace valve, See

ENGINES

Loose rocker arms

Retighten rocker arms,

See ENGINES

Excessive valve seat run-out

Reface valve seats, See

ENGINES

Missing valve lock

Install new valve lock

Excessively worn camshaft lobes

Replace camshaft, See

ENGINES

Plugged valve lifter oil holes

Eliminate restriction or

replace lifter

Faulty valve lifter check ball

Replace lifter check ball,

See ENGINES

Rocker arm nut installed upside down

Remove and reinstall

correctly

Valve lifter incorrect for engine

Remove and replace valve

lifters

Faulty push rod seat or lifter plunger

Replace plunger or push

rod

Noisy Valves

Improper valve lash

Re-adjust valve lash, See

ENGINES

Worn or dirty valve lifters

Clean and/or replace

lifters

Worn valve guides

Replace valve guides, See

ENGINES

2008 Chevrolet Silverado 1500

GENERAL INFORMATION Trouble Shooting - Basic Procedures

Excessive valve seat or face run-out

Reface seats or valve face

Worn camshaft lobes

Replace camshaft, See

ENGINES

Loose rocker arm studs

Re-tighten rocker arm

studs, See ENGINES

Bent push rods

Replace push rods, See

ENGINES

Broken valve springs

Replace valve springs, See

ENGINES

Burned,Sticking or Broken Valves

Weak valve springs or warped valves

Replace valves and/or

springs, See ENGINES

Improper lifter clearance

Re-adjust clearance or

replace lifters

Worn guides or improper guide clearance

Replace valve guides, See

ENGINES

Out-of-round valve seats or improper seat width

Re-grind valve seats

Gum deposits on valve stems, seats or guide

Remove deposits

Improper spark timing

Re-adjust spark timing

Broken Pistons/Rings

Undersize pistons

Replace with larger

pistons, See ENGINES

Wrong piston rings

Replace with correct

rings, See ENGINES

Out-of-round cylinder bore

Re-bore cylinder bore

Improper connecting rod alignment

Remove and realign

connecting rods

Excessively worn ring grooves

Replace pistons, See

ENGINES

Improperly assembled piston pins

Re-assemble pin-to-piston,

See ENGINES

Insufficient ring gap clearance

Install new rings, See

ENGINES

Engine overheating

Check cooling system

Incorrect ignition timing

Re-adjust ignition timing,

See TUNE-UP

Excessive Exhaust Noise

2008 Chevrolet Silverado 1500

GENERAL INFORMATION Trouble Shooting - Basic Procedures

ENGINE PERFORMANCE

CARBURETOR TROUBLE SHOOTING:

BASIC COLD START SYMPTOMS TROUBLE SHOOTING CHART

Leaks at manifold to head, or to pipe

Replace manifold or pipe

gasket

Exhaust manifold cracked or broken

Replace exhaust manifold,

See ENGINES

NOTE:

This is GENERAL information. This article is not intended to be
specific to any unique situation or individual vehicle configuration.
The purpose of this Trouble Shooting information is to provide a list
of common causes to problem symptoms. For model-specific
Trouble Shooting, refer to SUBJECT, DIAGNOSTIC, or TESTING
articles available in the section(s) you are accessing.

CONDITION & POSSIBLE CAUSE

CORRECTION

Engine Won't Start

Choke not closing

Check choke operation,

see FUEL SYSTEMS

Choke linkage bent

Check linkage, see FUEL

SYSTEM

Engine Starts, Then Dies

Choke vacuum kick setting too wide

Check setting and adjust

see, FUEL SYSTEMS

Fast idle RPM too low

Reset RPM to

specification, see TUNE-

UP

Fast idle cam index incorrect

Reset fast idle cam index,

see FUEL SYSTEMS

Vacuum leak

Inspect vacuum system for

leaks

Low fuel pump outlet

Repair or replace pump,

see FUEL SYSTEMS

Low carburetor fuel level

Check float setting see

FUEL SYSTEM

Engine Quits Under Load

2008 Chevrolet Silverado 1500

GENERAL INFORMATION Trouble Shooting - Basic Procedures

BASIC HOT START SYMPTOMS TROUBLE SHOOTING CHART

BASIC COLD ENGINE DRIVEABILITY SYMPTOMS TROUBLE SHOOTING
CHART

Choke vacuum kick setting incorrect

Reset vacuum kick

setting,see FUEL

SYSTEMS

Fast idle cam index incorrect

Reset fast idle cam index,

see FUEL SYSTEM

Incorrect hot fast idle speed RPM

Reset fast idle RPM, see

TUNE-UP

Engine Starts, Runs Up, Then Idles, Slowly With Black Smoke

Choke vacuum kick set too narrow

Reset vacuum kick, see

FUEL SYSTEMS

Fast idle cam index incorrect

Reset fast idle cam index,

see FUEL SYSTEMS

Hot fast idle RPM too low

Reset fast idle RPM, see

TUNE-UP

CONDITION & POSSIBLE CAUSE

CORRECTION

Engine Won't Start

Engine flooded

Allow fuel to evaporate

CONDITION & POSSIBLE CAUSE

CORRECTION

Engine Stalls in Gear

Choke vacuum kick setting incorrect

Reset choke vacuum kick,

see FUEL SYSTEMS

Fast idle RPM incorrect

Reset fast idle RPM, see

TUNE-UP

Fast idle cam index incorrect

Reset fast idle cam see

FUEL SYSTEMS

Acceleration Sag or Stall

Defective choke control switch

Replace choke control

switch

Choke vacuum kick setting incorrect

Reset choke vacuum kick

see, FUEL SYSTEMS

Float level incorrect (too low)

Adjust float level, FUEL

SYSTEMS

2008 Chevrolet Silverado 1500

GENERAL INFORMATION Trouble Shooting - Basic Procedures