A bigger spark plug gap is better as it increases the engine horsepower and performance but you also need an increase in voltage so you'll need a higher voltage ignition coil for the increase in gap if you go too large.
Normally if the spark plug gap is too big than specified for your vehicle then you may experience loss of power, misfires, spark plug fouling, increased plug wear, or poor gas mileage.
Too small of a gap in your spark plugs may give too weak of a spark to complete the combustion process within the engine; too wide of a gap can lead to the spark plug not firing correctly, causing misfires at high speeds.
To change a spark plug remove the spark plug wire and then place a spark plug socket over the spark plug until it seats onto the spark plug and then use a ratchet and remove the spark plug by moving the ratchet in the counter clockwise direction.
Sometimes spark plugs may be difficult to get too or they may be difficult to remove so you may need to use a pipe on your ratchet if possible for leverage.
Remove the Spark Plug Wire.
Remove the Coil On Plug (COP) if your has it.
Unscrew the Spark Plug.
Put in the New Spark Plugs.
Re-install the Spark Plug Wires or Ignition Coils (COP)
Start Up the Engine.
You can check a spark plug with a battery by connecting one end of the spark plug to the positive side of the battery and then connect a light tester tool to the negative side of the battery and then touch the positive end of the tester to the spark plug and if the light comes on then the spark plug is most likely good and if not the spark plug is usually bad.
Another way to check spark plugs is to pull a plug wire, clip on the spark tester, crank the motor and look for spark jumping the gap, right? There's an easier way: the OK Spark plug tester.
Just hold the tester's probe near a plug wire (or even near a coil-on-plug coil assembly) and you can tell if the plug is firing.
The life of a spark plug is around 30,000 to 90,000 miles although some spark plugs are good for around 100,000 to 120,000 miles before needing replaced.
Spark plugs do affect acceleration.
If spark plugs are bad or weak they can cause poor acceleration and engine hesitation as well as misfiring of the engine and even hard starting.
Spark plugs should be replaced every 30,000 to 90,000 miles although some spark plugs can last as long as 100,000 miles to 120,000 miles or when your vehicle starts showing signs that the spark plugs are bad.
Signs that you need to replace spark plugs include.
Your car is a rough starter.
Your car is a rough idler.
Your engine will sometimes misfire.
Your engine surges.
Your fuel consumption is higher than usual.
Your car isn't accelerating as it should.
When your car shakes after you changed the spark plugs it could be caused by weak coils that are producing low voltage to create enough spark for your new spark plugs.
Also your spark plugs may not be gapped properly.
Other things such as a faulty idle air control valve may cause the engine idle to drop below the normal idling RPM which may also cause the motor to shake or vibrate more than normal.
Orange spark is caused by weak spark and low voltage going to the spark plugs.
Most often an orange or weak spark is caused by bad ignition coils, weak ignition coils, bad ignition control module etc.
The strength of the spark is revealed in the color.
A red or yellow spark is weak and probably will not spark in the cylinder.
A blue or white spark is strong and has enough voltage to fight across the spark plug gap even under pressure within the cylinder.
When replacing spark plugs you should replace ignition coils for the best performance.
If it's time to replace spark plugs then the ignition coils are likely to fail soon anyway so while you have to unplug the ignition coils from the spark plugs it's best to replace the ignition coils with the spark plugs.
To check a spark ignition coil you can remove the coil or plug wire from the spark plug and insert a screwdriver and lay the screwdriver against the engine and crank the engine to check for spark.
Weak spark or no spark is likely a result of the bad ignition coil.
You can also check a spark ignition coil using a multimeter.
Ignition coils have two circuits that require checking; primary and secondary circuits.
Connect the multimeter to the negative and positive terminals of the ignition coil to get a primary circuit reading.
If the multimeter shows a reading of 0 ohms, the ignition coil has shorted and needs replacing.
A low battery could cause weak spark if the battery does not have enough voltage or power to allow the ignition coil to step up the voltage.
However if the battery is up enough to crank the engine then it should be good enough to create enough spark to get the engine started.
Weak spark can be caused by bad ignition coils, bad ignition control module, bad spark plugs, bad spark plug wires, bad distributor, bad distributor cap, bad distributor rotor etc.
A weak spark, or no-spark, problem may originate within one or more common ignition system components: Worn or damaged spark plug wire insulation.
At high temperature, this problem can produce bucking or misfires. Dirty or worn spark plug.
The alternator does not fire the spark plugs directly.
The alternator keeps voltage producing to the battery as well as the ignition system and the vehicles electrical system.
That electricity is then used to supply the vehicle with power and also send voltage to the ignition coil which then steps up the voltage from the 12 volts to the thousands of volts needed to fire the spark plugs and ignite the fuel.
The ignition coil along with the spark plugs, ignition control module and sometimes a distributor if your car has one is responsible for firing the spark plugs and igniting the fuel.
12 volt ignition coils work by increasing the voltage from the cars battery and alternator and the coil sends the high voltage to the spark plugs to ignite the fuel.
In order to produce the required high voltages the 12 volt ignition coils make use of the relationships that exist between electricity and magnetism.
When an electric current flows through an electrical conductor such as a coil of wire, it creates a magnetic field around the coil.
To test a coil or ignition coil with a screwdriver remove the coil from the spark plug and place a screwdriver into the plug of the coil that plugs into the spark plug.
Then rest the screwdriver against the engine so that it grounds out.
Then crank the engine and look for spark and if you have weak spark or no spark the ignition coil is likely bad.
If you have spark plug wires and one coil then take the screwdriver and place it into one of the spark plug wires and place the screwdriver against the engine and crank the engine again and look for spark.
When a spark plug coil is bad it will cause the engine to misfire and can even sometimes cause hard engine starting.
Although most commonly you'll get a misfire on a certain cylinder that the ignition coil is on.
Some ignition coils have oil in them to dissipate the heat and if your ignition coil has oil on it then it likely is going bad and the oil has made a way through a crack in the ignition coil.
Another reason for the oil on the ignition coil is because of oil leaking from your engine or you spilled oil on the ignition coil without knowing it.
A bad ignition coil will cause a vehicle to not start if it's a vehicle that has one ignition coil.
If the vehicle has more than one ignition coil then the car should start on the other cylinders but will misfire on the bad ignition coil.
Other causes of car not starting include, bad fuel pump, bad spark plugs, bad fuel injectors, low fuel pressure, clogged fuel filter etc.
When ignition coils fail your car or other vehicle may be hard to start, not start at all, have loss of engine power, engine shaking, use more fuel, misfire.