• 2016


There are a group of engine and related parts that require routine maintenance. While engine fluids are checked and replaced, more often, spark plugs are not changed nearly as often as engine oil. Some focus must be on the inspection and replacement of engine parts. These components include air and cabin filters, spark plugs and ignition cables.


A dirty engine air filter can have a significant impact on both performance and fuel economy. In order for fuel to burn efficiently and produce power in the cylinder, air is required. If an engine cannot breathe freely, it cannot operate efficiently. Furthermore, the amount of power produced by an engine is directly proportional to the amount of air that can be put into it. That’s why turbochargers and superchargers are used to increase horsepower. These devices are not adding fuel, but adding air.

If the air filter is dirty, the amount of air that can enter the engine is restricted. This reduces power and fuel economy. It’s that simple. Figure 1 shows a typical dirty air filter.

As a general rule, air filters should be replaced every 15,000 miles, which is about once a year. If the vehicle is operated in extreme environments (for example, off-roading with your Jeep. Wrangler), the air filter should be inspected and replaced more often. It’s a good bet that all that driving in the woods will clog the air filter quicker than the everyday driving. If your customer is going to do one maintenance task per year to maintain engine performance, it should be changing the air filter.


Depending on driving style and local weather, many of your customers might drive with the windows closed most of the time. If the recirculation button is turned on, (as it is when Max A/C is selected) your customer is not breathing very fresh air. Fortunately, many, but not all, FCA US LLC vehicles are equipped with a cabin air filter that helps purify the outside air entering the HVAC housing.

The filter is mounted in the engine compartment, inside of the fresh air inlet housing of the heating-A/C system. The filter should be replaced at least every 15,000 miles, or each year, and checked if heating- A/C system performance seems lower than expected. The cabin air filter is labeled with Rear of Vehicle and an arrow to indicate air flow direction through the filter. Make sure to properly install the cabin air filter. Failure to properly install the filter will result in the need to replace the filter sooner than required by design.

Replacing the cabin air filter varies from vehicle-to-vehicle. On the Challenger/Charger and 300 models, the filter is replaced outside of the car through the cowl opening. On other vehicles, such as the minivans and the Dodge Dart, the filter is replaced inside the vehicle. In some cases, the glove box must be removed. Check the appropriate manual for the vehicle being serviced.

Note: It is important to keep the air intake opening clear of debris, like dust and leaf particles, that are small enough to pass through the cowl opening screen and can accumulate within the HVAC housing. This environment created within the housing is ideal for the growth of certain molds, mildews and other fungi. Any accumulation of decaying plant matter provides an additional food source for fungal spores, which enter the housing with the fresh intake-air; excess debris, as well as objectionable odors created by decaying plant matter and growing fungi that can be discharged into the passenger compartment during heater-A/C operation, if the air intake opening is not kept clear of dirt and debris.


You don’t have to go back too many years to find a time when spark plugs were changed on a regular basis. The great Dodge, Plymouth and Chrysler Brand muscle cars of the ‘60s and ‘70s chewed up spark plugs and spit ‘em out. Thankfully, those days are gone. The modern spark plug, thanks to the use of advanced materials, the removal of lead from gasoline and improved combustion efficiency, last for many years and tens of thousands of miles.

Another advance in ignition technology is the system known as coil on plug. The system’s four main components are the coils, crankshaft position sensor, spark plugs, and camshaft position sensors. The coil on plug ignition system utilizes an ignition coil for every cylinder. The ignition coils are mounted directly over each spark plug. As a result, ignition cables are no longer required.

Inspection and replacement intervals for spark plugs, and ignition cables, if used, have been significantly extended since the muscle car era. For late model engines such as the 3.6L VVT V6, the 5.7L/6.4L HEMI. engines and the 2.4L MultiAir., the replacement interval is 100,000 miles. There is no time interval requirement, only mileage.

Note: Many of these newer engines use platinum spark plugs; care must be used when cleaning this type of plug as cleaning might damage the platinum center electrode or thin the platinum pad.

The service interval for older engines, such as the 2.4L commonly used in the PT Cruiser, the 3.3L/3.8L V6s that were the mainstay in the minivans and the 3.7L V6/4.7L V8 Magnum engines vary from engine-to-engine.

spark_plugsA spark plug from the 2.4L 4 cylinder in a 2002 PT Cruiser that exceeded the recommended replacement interval and a brand new plug, side-by-side.


Schedule B is used for vehicles that are operated under the conditions listed below:

Day or night temperatures are below 32° F

Stop and go driving

Extensive engine idling

Driving in dusty conditions

Short trips of less than 10 miles

More than 50% of driving is at sustained high speeds during hot weather, above 90° F

Trailer towing

Taxi, police, or delivery service

Off-road or desert operation

If the vehicle is not operated under any of the above conditions, follow Schedule A. For example, the Schedule A recommended interval for spark plug replacement for the 3.3L/3.8L V6 is 75,000 miles. If you follow Schedule B, the interval is 60,000. As always, when in doubt, refer to the manual for the vehicle being serviced.