Honda Civic. Manual — part 315

BASIC SPARK PLUG TROUBLE SHOOTING CHARTS

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

Normal Spark Plug Condition

Light Tan or Gray deposits

No Action

Electrode not burned or fouled

No Action

Gap tolerance not changed

No Action

Cold Fouling or Carbon Deposits

Overrich air/fuel mixture

Adjust air/fuel

mixture, see ENGINE

PERFORMANCE

section

Faulty choke

Replace choke

assembly, see

ENGINE

PERFORMANCE

section

Clogged air filter

Clean and/or replace

air filter

Incorrect idle speed or dirty carburetor

Reset idle speed and/

or clean carburetor

Faulty ignition wires

Replace ignition

wiring

Prolonged operation at idle

Shut engine off during

long idle

Sticking valves or worn valve guide seals

Check valve train

Wet Fouling or Oil Deposits

Worn rings and pistons

Install new rings and

pistons

Excessive cylinder wear

Rebore or replace

2008 Honda Civic EX

GENERAL INFORMATION Trouble Shooting - Basic Procedures

block

Excessive valve guide clearance

Worn or loose bearing

Gap Bridged

Deposits in combustion chamber becoming fused
to electrode

Clean combustion

chamber of deposits

Blistered Electrode

Engine overheating

Check cooling system

Wrong type of fuel

Replace with correct

fuel

Loose spark plugs

Retighten spark plugs

Over-advanced ignition timing

Reset ignition timing

see ENGINE

PERFORMANCE

Pre-Ignition or Melted Electrodes

Incorrect type of fuel

Replace with correct

fuel

Incorrect ignition timing

Reset ignition timing

see ENGINE

PERFORMANCE

Burned valves

Replace valves

Engine Overheating

Check cooling system

Wrong type of spark plug, too hot

Replace with correct

spark plug, see

ENGINE

PERFORMANCE

Chipped Insulators

Severe detonation

Check for over-

advanced timing or

combustion

Improper gapping procedure

Re-gap spark plugs

Rust Colored Deposits

Additives in unleaded fuel

Try different fuel

brand

2008 Honda Civic EX

GENERAL INFORMATION Trouble Shooting - Basic Procedures

BASIC ELECTRONIC IGNITION TROUBLE SHOOTING CHARTS

Water In Combustion Chamber

Blown head gasket or cracked head

Repair or replace head

or head gasket

NOTE:

Before diagnosing an electronic ignition system, ensure
that all wiring is connected properly between distributor,
wiring connector and spark plugs. Ignition problem will
show up either as: Engine Will Not Start or Engine Runs
Rough.

CONDITION & POSSIBLE CAUSE

CORRECTION

Engine Won't Start

Open circuit between distributor and bulkhead
connector

Repair circuit

Open circuit between bulkhead connector and
ignition switch

Repair circuit

Open circuit between ignition switch and starter
solenoid

Repair circuit

Engine Runs Rough

Fuel lines leaking or clogged

Tighten fitting,

remove restriction

Initial timing incorrect

Reset ignition timing

see ENGINE

PERFORMANCE

Centrifugal advance malfunction

Repair distributor

advance

Defective spark plugs or wiring

Replace plugs or plug

wiring

Component Failure

Spark arc-over on cap, rotor or coil

Replace cap, rotor or

or coil

Defective pick-up coil

Replace pick-up coil

2008 Honda Civic EX

GENERAL INFORMATION Trouble Shooting - Basic Procedures

BASIC ELECTRONIC IGNITION TROUBLE SHOOTING CHARTS -
USING OSCILLOSCOPE PATTERNS

Defective ignition coil

Replace ignition coil

Defective vacuum unit

Replace vacuum unit

Defective control module

Replace control

module

CONDITION & POSSIBLE CAUSE

CORRECTION

Firing Voltage Lines are the Same, but Abnormally High

Retarded ignition timing

Reset ignition timing,

see ENGINE

PERFORMANCE

section

Fuel mixture too lean

Readjust carburetor,

see ENGINE

PERFORMANCE

High resistance in coil wire

Replace coil wire

Corrosion in coil tower terminal

Clean and/or replace

coil

Corrosion in distributor coil terminal

Clean and/or replace

distributor cap

Firing Voltage Lines are the Same but Abnormally Low

Fuel mixture too rich

Readjust carburetor,

see ENGINE

PERFORMANCE

Breaks in coil wire causing arcing

Replace coil wire

Cracked coil tower causing arcing

Replace coil

Low coil output

Replace coil

Low engine compression

Determine cause and

repair

One or More, But Not All Firing Voltage Lines are Higher Than Others

Carburetor idle mixture not balanced

Readjust carburetor,

see ENGINE

2008 Honda Civic EX

GENERAL INFORMATION Trouble Shooting - Basic Procedures