Last week we walked you through the process of replacing your spark plugs! In passing I mentioned that its worth inspecting the old plugs as these can reveal a great deal of information about the health of your engine.
 
In this week’s article, let us elaborate on the different spark plug problem, the symptoms and the remedies.
 

NORMAL

(Using Unleaded Petrol)

 

NORMAL

(Using Lead Replacement Petrol)

 

PROBLEMS

 

1. CARBON FOULING

Typical Symptoms: 

• Hard starting

• Misfiring

• Black exhaust smoke

 

Causes:

• Rich mixture

• Retarded ignition
• Low compression
• Too cold a spark plug
Remedy:

• Check float level

• Check choke

• Check ignition timing

• Check air cleaner

• Check compression

• Replace spark plug with correct heat range

 

 

2. OIL FOULED

Typical Symptoms: 

• Hard starting

• Misfiring

• Grey / white exhaust smoke

• Loss of oil

 

Causes:

• Worn rings

• Worn piston
• Leaking valve stem seals
• Over-filled oil sump
Remedy:

• Replace worn components

• Replace spark plug with correct heat range

 

3. DEPOSIT

Typical Symptoms: 

• Misfiring

• Hard starting

• No starting

 

Causes:

• Fuel quality

• Oil leakage
• Engine operating period
Remedy:

• Replace spark plug

• Change fuel brand

• Repair engine (if need be)

 

4.BREAKAGE OF THE INSULATOR

Typical Symptoms: 

• Misfiring

• Engine noise

 

Causes:

• Sudden change in temperature (Thermal shock)

• Oil leakage
• Internal engine stress

Remedy:

• Check jets are not clogged

• Check float level

• Check ignition timing

• Replace spark plug with correct heat range

 

5. OVERHEATING

Typical Symptoms: 

• "Pinking" under acceleration or climbing hills

• Engine run-on after switching off

 

Causes:

• Lean mixture 
• Advanced ignition timing
• Too hot a spark plug

 

Remedy:

• Check jets are not clogged

• Check float level

• Check ignition timing

• Replace spark plug with correct heat range

 

6. DAMAGED

Typical Symptoms: 

• Misfiring

• Loss of power
• Hard starting
• Noise in engine

 

Causes:

• Foreign particles inside cylinder
• Broken or damaged valve

Remedy:

• Replace spark plugs

• Remove foreign or damaged components

 

7. UNDER TIGHTENING

Typical Symptoms: 

• Hard starting

• Misfiring
• Black exhaust smoke

Causes:

• Incorrectly torqued

• Spark plug only hand tightened

• Dirt or carbon in threads of cylinder head

Remedy:

• Replace spark plugs

• Tighten spark plug to correct torque

• Replace damaged components

• Check compression on all cylinders

 

8. WORN

Typical Symptoms: 

• Hard starting

• Reduced fuel economy

Causes:

• Normal electrode wear • ± 0.03mm / 1000km

• Fuel deposits (carbon, lead, additives & salts)

Remedy:

• Replace spark plug with correct heat range

 

9. MELTING

Typical Symptoms: 

• Hard starting

• Misfiring

Causes:

• Lean mixture

• Advanced ignition timing
• To hot heat range

Remedy:

• Replace with correct heat range spark plug

• Check air / fuel mixture

 

10. BREAKAGE OF THE GROUND ELECTRODE

Typical Symptoms: 

• Misfiring
• Loss of power
• Noise in engine

Causes:

• Under tightening

Remedy:

• Correct tightening torques

 

11. FOULING BY FUEL ADDITIVE

Typical Symptoms: 

• Misfiring
• Hard starting
• Reduced fuel economy

Causes:

• Excess MMT and Ferrocene

• Incorrect heat range

Remedy:

• Replace spark plugs with correct heat range

• Get to 450°C self cleaning temperature

 

Summary

 

A worn spark plug not only wastes fuel but also strains the whole ignition system because the expanded gap requires higher voltage. It also reduces the engine's efficiency, resulting in reduced fuel economy and increased exhaust emissions. Moreover, it contributes to pollution generated by exhaust gas.

 

Head over to Startmycar.co.za for all your replacement spark plug needs!