Engine Repair

How to know when to Replace Spark Plugs



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Spark plugs ought to be changed out at standard service intervals but exactly how do you know when to replace them in the event the engine is operating poorly?

A few indications would be: a decrease in fuel mileage or acquiring an engine miss. Both of these items are certainly symptoms of faulty spark plugs, however they might not always be the issue. Your most effective method to confirm a defective spark plug is to use an oscilloscope which can be connected to the ignition system and can produce a picture of each and every spark plug firing, similar to a heart beat.This will more than likely need to be accomplished at an automotive shop. An oscilloscope is an expensive device and much like a doctor you need to be capable to comprehend the readings you are receiving.

The majority of motor vehicles nowadays can certainly function 100,000 miles on a set of plugs. In case your car is an older model and does not use platinum sprark plugs the standard interval to change a set of spark plugs is every 30,000 miles to maintain fuel efficiency at it's optimum. These are simply typical routine maintenance intervals if you're having overall performance issues with your car then spark plugs could be the reason.

Since you will most likely not have an oscilloscope here are a few actions you can take manually to evaluate your problem.  It's not as simple as it used to be to determine when the spark plugs need changed due to an engine miss. These days quite a few engines possess the "coil over" ignition system and it's somewhat more difficult to determine what produces the misfire. In addition to that, with electronic engine controls, the computer may compensate for an engine miss and disguise it as something else entirely.

Should you have a great deal of miles on a set of spark plugs and your engine is operating poorly, it might be a good starting point to try to repair the problem. Since you may need a fresh set anyway you wouldn't be out anything to go ahead and replace all of them.

Certainly if you pull a couple of plugs out and physically examine them you could make an even better determination on whether or not they will need replaced. Every spark plug which has the electrode in the center of the plug worn out needs replaced. In the event the plug has major carbon deposits on it then it needs replaced, however you might have an even deeper issue with oil consumption. If the grounding electrode on the plug is bent or broken you will need to change it without a doubt. If the spark plugs have a great deal of miles on them you would then want to replace them as a set, not just the ones that have failed.

Certainly the easiest method to determine if there is a spark plug misfire problem is to take it to a garage which has an oscilloscope where they are able to tell just how the spark plugs are firing. They are able to evaluate the firing pattern without needing to remove the spark plugs. This saves considerable time however, you will most likely have to pay someone to do this.

Last but not least look at your owner's manual to see whether it provides you with a spark plug change interval. Make an effort to replace the plugs using the original manufacturers specifications unless of course they have updated them through a service bulletin. Check your local dealer for service bulletin updates, however, many times typical garages as well as parts stores will have this information through the help of computer technology.

Spark plugs are certainly not as serviceable of an item as they were in the past, however that does not mean you should not pay attention to them.

More about this author: Mike Webb

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