Chevrolet Silverado / GMC Sierra. Service manual — part 1220

Improper ignition timing

Reset ignition timing, See

TUNE-UP

Faulty accelerator pump discharge

Replace accelerator pump

Improper choke operation

Check choke and adjust as

required

Defective EGR valve

Replace EGR valve

Fuel mixture too lean

Reset air/fuel mixture, See

TUNE-UP

Choke valve initial clearance too large

Reset choke valve initial

clearance

Exhaust Backfire

Vacuum leak

Inspect and repair vacuum

system

Faulty vacuum diverter valve

Replace vacuum diverter

valve

Faulty choke operation

Check choke and adjust as

required

Exhaust system leak

repair exhaust system leak

Engine Detonation

Ignition timing too far advanced

Reset ignition timing, See

TUNE-UP

Faulty ignition system

Check ignition timing, See

TUNE-UP

Spark plugs loose or faulty

Retighten or replace plugs

Fuel delivery system clogged

Inspect lines, pump and

filter for clog

EGR valve inoperative

Replace EGR valve

PCV system inoperative

Inspect and/or replace

hoses or valve

Vacuum leaks

Check vacuum system and

repair leaks

Excessive combustion chamber deposits

Remove built-up deposits

Leaking, sticking or broken valves

Inspect and/or replace

valves

External Oil Leakage

Fuel pump improperly seated or worn gasket

Remove pump, replace

gasket and seat properly

2008 Chevrolet Silverado 1500

GENERAL INFORMATION Trouble Shooting - Basic Procedures

Oil pan gasket broken or pan bent

Straighten pan and replace

gasket

Timing chain cover gasket broken

Replace timing chain

cover gasket

Rear main oil seal worn

Replace rear main oil seal

Oil pan drain plug not seated properly

Remove and reinstall

drain plug

Camshaft bearing drain hole blocked

Remove restriction

Oil pressure sending switch leaking

Remove and reinstall

sending switch

Excessive Oil Consumption

Worn valve stems or guides

Replace stems or guides,

See ENGINES

Valve "O" ring seals damaged

Replace "O" ring seals,

See ENGINES

Plugged oil drain back holes

Remove restrictions

Improper PCV valve operation

Replace PCV valve

Engine oil level too high

Remove excess oil

Engine oil too thin

Replace thicker oil

Valve stem oil deflectors damaged

Replace oil deflectors

Incorrect piston rings

Replace piston rings, See

ENGINES

Piston ring gaps not staggered

Reinstall piston rings, See

ENGINES

Insufficient piston ring tension

Replace rings, See

ENGINES

Piston ring grooves or oil return

slots clogged Replace

piston rings, See

ENGINES

Piston rings sticking in grooves

Replace piston rings, See

ENGINES

Piston ring grooves excessively worn

Replace piston and rings,

See ENGINES

Compression rings installed upside down

Replace compression rings

correctly, See ENGINES

Worn or scored cylinder walls

Rebore cylinders or

replace block

2008 Chevrolet Silverado 1500

GENERAL INFORMATION Trouble Shooting - Basic Procedures

Mismatched oil ring expander and rail

Replace oil ring expander

and rail, See ENGINES

Intake gasket dowels too long

Replace intake gasket

dowels

Excessive main or connecting rod bearing clearance

Replace main or

connecting rod bearings,

See ENGINES

No Oil Pressure

Low oil level

Add oil to proper level

Oil pressure sender or gauge broken

Replace sender or gauge

Oil pump malfunction

Remove and overhaul oil

pump, See ENGINES

Oil pressure relief valve sticking

Remove and reinstall

valve

Oil pump passages blocked

Overhaul oil pump, See

ENGINES

Oil pickup screen or tube blocked

Remove restriction

Loose oil inlet tube

Tighten oil inlet tube

Loose camshaft bearings

Replace camshaft

bearings, See ENGINES

Internal leakage at oil passages

Replace block or cylinder

head

Low Oil Pressure

Low engine oil level

Add oil to proper level

Engine oil too thin

Remove and replace with

thicker oil

Excessive oil pump clearance

Reduce oil pump

clearance, See ENGINES

Oil pickup tube or screen blocked

Remove restrictions

Main, rod or cam bearing clearance excessive

Replace bearing to reduce

clearance, See ENGINES

High Oil Pressure

Improper grade of oil

Replace with proper oil

Oil pressure relief valve stuck closed

Eliminate binding

Oil pressure sender or gauge faulty

Replace sender or gauge

Noisy Main Bearings

2008 Chevrolet Silverado 1500

GENERAL INFORMATION Trouble Shooting - Basic Procedures

Inadequate oil supply

Check oil delivery to main

bearings

Excessive main bearing clearance

Replace main bearings,

See ENGINES

Excessive crankshaft end play

Replace crankshaft, See

ENGINES

Loose flywheel or torque converter

Tighten attaching bolts

Loose or damaged vibration damper

Tighten or replace

vibration damper

Crankshaft journals out-of-round

Re-grind crankshaft

journals

Excessive belt tension

Loosen belt tension

Noisy Connecting Rods

Excessive bearing clearance or missing bearing

Replace bearing, See

ENGINES

Crankshaft rod journal out-of-round

Re-grind crankshaft

journal

Misaligned connecting rod or cap

Remove rod or cap and

realign

Incorrectly tightened rod bolts

Remove and re-tighten rod

bolts

Noisy Pistons and Rings

Excessive piston-to-bore clearance

Install larger pistons, See

ENGINES

Bore tapered or out-of-round

Rebore block

Piston ring broken

Replace piston rings, See

ENGINES

Piston pin loose or seized

Replace piston pin, See

ENGINES

Connecting rods misaligned

Realign connecting rods

Ring side clearance too loose or tight

Replace with larger or

smaller rings

Carbon build-up on piston

Remove carbon

Noisy Valve Train

Worn or bent push rods

Replace push rods, See

ENGINES

Worn rocker arms or bridged pivots

Replace push rods, See

2008 Chevrolet Silverado 1500

GENERAL INFORMATION Trouble Shooting - Basic Procedures