Fix It

While the computerized engine management systems that run todays cars are extremely complex and require increasing specialized diagnostic equipment and tools, all gasoline-burning engines must still have spark plugs. The plugs allow a properly timed spark of electricity to jump through the flammable mixture introduced into the top of the piston chamber, causing ignition. Ascertaining their condition is done more through familiarity and interpretive knowledge than through the use of a single piece of equipment.

Know Your Plugs

The terms cold plug and hot plug are often used, and a knowledge of what to expect from the plug is necessary in determining its condition. The terms er to the ability of the material that the plug is made from to transfer heat, in this instance from the point at which the spark occurs into the engine block for dissipation. A cold plug transfers heat quickly and does not work well at extremely high temperatures. A hot plug transfers heat poorly, allowing heat to build up to approximately 1,550 degrees Fahrenheit, and is designed to work in that way; hot plugs are less susceptible to fouling because they burn off contamination. Identification is a question of experience: In general, hot plugs have longer insulator tips.

Visual Condition

Always allow an engine to fully cool before attempting any service work, including the removal of spark plugs. If the insulator tip of a plug that has been in service looks pale gray, or pale gray with a yellow or brown tint, the engine is running correctly, the spark plug gap is set correctly and the plug is torqued correctly into the receiver. Dull, black carbonization on the tip suggests that too-cold plugs are in use, and they should be replaced with hotter-running units. As with all visual indications, this symptom could also indicate problems elsewhere in the engine, in this instance a bad fuel mixture. Melting at the electrode indicates either that the plug was incorrectly torqued into position or that the heat range of the plug is not as suggested for the engine.

Gapping

The space between the electrode and the insulator tip must be exact for the plug to function correctly. Spark plug gap-testing tools are a set of wafer-thin blades -- each blade looks something like a fingernail cleaner -- that rotate on a pivot in and out of a case. These tools used to be ubiquitous in every do-it-yourselfers and professionals kit, but modern engines and plug technology have made them all but redundant. New plugs are now delivered with the gap precisely set and do not deform under any but the most extreme of engine conditions. If a modern spark plug gap changes under use, that is a symptom, not a cause; the cause must be determined by engine diagnostics and the plug set replaced after rectification of the fault.

Equipment

An array of equipment is available to test spark plug condition, but the visual checks suggested and a regular maintenance schedule make the investment practically unnecessary, even for the professional. The spark plug gapping tool is, as noted, all but redundant in modern vehicle maintenance practices. Working according to the manufacturers instructions, it is possible to use a volt-ohmmeter to ascertain the circuit load.

Voltage Testing

Metered spark gap testers are available that plug into the coil to measure the jump of the spark. Capable of handling current between 0 and 40,000 volts, the tool diagnoses faults in the coil, the ignition wires and the plugs.

Testing Spark Plug Wires

Inline spark testers that use a bulb do not give a metered reading, but they do give an instant indication of whether a coil-wire-plug circuit is operational. The device is inserted between the plug and the wire, after you have first removed the wire from the top of the plug. When the engine is turned over a bulb flashes if the circuit is functional but does not flash if it is faulty. Compact ignition testers are extremely simple to use to verify that there is a spark to the plug. Fitted into a plug wire end and clamped to the engine, they should spark when the engine is turned over. If they do not, there is a problem upstream of the device.

Several problems plague the instrument clusters in vehicles of every make, model and year. These problems become more difficult to fix as cars themselves become more complex and computerized. Older cars merely required tinkering with a plug or smacking the top of the dashboard to "fix" the problem. Newer cars often require full replacement of the entire instrument cluster, which can cost hundreds of dollars.

Full Replacement

Full replacement of the instrument cluster requires a mechanic to remove the entire dashboard and steering column to remove the instrument cluster. The part is then replaced and the entire dashboard must be replaced. This simple removal and replacement can take hours to complete since it requires so much work to get to the part. New or used, the cluster is very pricey considering its function. Some models of used instrument cluster can be found on sites such as eBay Motors for about $100, though these often come with no guarantee or return policy. New instrument clusters cost between $400 and $1,500, depending on the year, make and model of the vehicle.

Cosmetic Repairs

Cosmetic repairs, such as repainting or replacing worn out needles or replacing a bulb thats gone bad in a digital odometer, are just as difficult as replacing the entire instrument cluster. In fact, many mechanics suggest simply replacing the entire instrument cluster when this happens because they must go through the same motions anyway. However, if you do not mind having an exposed instrument panel, the fiberglass dust panel may be removed for easier access to the needles. The needles are made of hard plastic, but a paint like Testors or similar model paint will work to repaint this surface. Panels that have warped or broken because of an accident or heat must be fully replaced.

Non-Replacement Repairs

Instrument clusters are made of two small computer modules that connect to the vehicles main computer via a system of wires in later model cars. In older cars, the system is mostly pressure hoses with a few wires running into the transmission, engine and other areas of the vehicle. The computer modules can be replaced on their own. However, this too includes removing the entire dash from the car to get to these modules, which are located on the back of the instrument cluster. The wires and hoses on older models of vehicles can be replaced by snipping them off and connecting new ones.

Gauges on the instrument panel of your vehicle serve as safety indicators for speed, fuel and engine malfunction. The first padded instrument panel was introduced in 1956 as part of a safety campaign by Robert McNamara. Fast forward to the 2000s and all symbols on the instrument panel flash briefly upon starting, but a light that is constantly on or flashing needs immediate attention.

Electronic Throttle Control Warning Light

According to the Dodge Charger owners manual, the lightning bolt symbol on a Dodge Charger is the indicator for the electronic throttle control. The electronic throttle control regulates engine idle speed, traction control and cruise.

Warning Indicator Solid Light

If the lightning bolt on the instrument panel lights up and stays lit when the engine is running, stop the vehicle as soon as possible. The vehicle will be drivable, but see an authorized dealer without delay.

Warning Indicator Flashing Light

If the electronic throttle control light is on solid, completely stop the vehicle and put it in park. The warning light should turn off by cycling the ignition key. If the light comes on again and flashes when the engine is running, the car should be immediately serviced. The engine could stall or have a very rough idle and may need to be towed.