Car Engine Basics

A glance at those engines that let us down or lose power because of bad firing. Close up on tune-ups.

The Spark

The term refers to the passage of a high-tension current through the spark plugs, which in turn produces the needed spark to ignite the air-fuel mixture inside the combustion chamber. When an engine is not firing properly, the engine will either lose power*, stop idling properly* (constantly changing revs or a lumpy idle) or not start altogether because of some malfunction.

The idea

The engine works thanks to the combustion of the air/fuel mix. The Engine Control Unit (ECU) calculates the amount of air it needs to let in for the fuel to vaporize properly when you press on the gas pedal. A signal, or a spark, then ignites the mixture in the combustion chamber. On fuel-injected engines, the signal for the spark comes from the distributor cap or from the coil pack and then on to the spark plug.

Irregular idle

A tell-tale sign of bad firing is a varying engine idle. The problem doesn't actually come from a bad spark - it's simply misreadings from the ECU. First, it ups the engine's speed because intake manifold sensors are not detecting enough air. Then, the ECU senses too much carbon dioxide, so reacts with the opposite - reducing engine speed.

Tune-up

"Tune-up" refers to the act of changing the spark plugs. They are parts that wear out: the plug's anode wears down a little bit every time it fires, so in time, it disappears completely. Check official manufacturer recommendations to know exactly how often you should tune your car up.

Choosing your spark plugs: "best" may not be better

Spark plugs with anodes made of many different materials are available on the market. You can choose from carbon (metalloid), cooper or platinum. Many people tend to think platinum is necessarily the best, longest lasting option.

The fact of the matter is it's not always the better choice. It depends on your vehicle. So check before buying what's best for yours. Most cars only need carbon plugs, so why pay double for something that is unnecessary?

Easy to do

Usually, spark plugs are easily accessible. Then, all you need to do is pull on the plug's cable and, using your ratchet, take the plug out. The last socket kit I bought included special spark plug socket, both metric and imperial, which are long and fitted with a rubber inside to ease you job.

Once the old ones are out, put the new ones in, tighten (firmly but not excessively) and reconnect the cables. Very easy!

Distributor cap pains

Your problem could also have something to do, if you have an injected engine, with the distributor cap. Three sections of it may cause you some pain: for more, check the: Is it firing? Distributor cap article. It will be online shortly.

*Such symptoms may also originate from other problems.