Ignition and Engine Management

It Starts With A Spark

Most modern cars with four-stroke engines feature a mechanically timed electrical system for ignition. The distributor routes high-voltage current from the ignition coils to the spark plugs in synchronized firing order for the correct amount of time. The fuel must be ignited at the correct time to optimize the power created from the explosion.

The spark plugs must take the voltage produced by the ignition coils and create the spark required to ignite the fuel/air mix at a precise time. The parts of a modern spark plug are:

• Terminal
• Insulator
• Ribs
• Insulator Tip
• Seals
• Shell
• Central Electrode
• Ground Electrode

The gap in a spark plug may need to be adjusted, as a gap that is too narrow would produce a smaller or weaker spark and therefore won't effectively ignite the fuel/air mix. If the gap is too wide, the spark may not be created, especially at high speeds. Be sure to check out NAPA AUTO PARTS huge selection of spark plugs and spark plug gap gauges. Symptoms of a bad spark plug include a rough idle (a 'jittery' feeling while idling), engine surges, poor gas mileage and lack of acceleration.

As you drive your Chevrolet Tahoe for longer and longer, the high-voltage pulses from the ignition coil or distributor will eventually cause the plugs and the plug wires to burn out. If your spark plugs are working but you notice rough idling or misfires, you can test your spark plug wires. You can do an insulation test and mimic the driving conditions of a rainy day by spraying the plug wires with water while the engine is running. If the engine miss fires, you know the insulation on the wires is faulty or leaking.

A resistance test involves testing the internal conductor. Unplug both ends of one spark plug wire for a single cylinder, and measure the length of wire with string. Then, measure the string with a multimeter to tell if the circuit is open, so no spark goes to that cylinder.

Put Your Ignition Coils To The Test

Ignition coils utilize induction to turn the vehicle's battery voltage into a powerful current that produces a spark, which ignites the compressed fuel-air mix inside the combustion chamber, creating power and driving the piston down. Most modern cars use a single coil for each piston, depending on the manufacturer. Over time, those coils can wear out and fail, especially if corrosion or moisture is present or driving conditions are hot. Failing spark plugs can also cause coils to wear faster. Symptoms of a bad ignition coil can range from inability to start your car to a distinct misfiring when you accelerate. This can result in gas mileage loss or even black smoke emitting from the tailpipe.

If you're wondering how to test an ignition coil, it's easy. On most cars, when an ignition coil has gone bad, the check engine light will illuminate. Using a scan tool or diagnostic tool will provide the code you need to determine which coil or coils have gone bad. The issue could be the spark plugs or the ignition coil, so you can use an inline spark tester that will tell you if the coil is delivering electricity to the spark plug or not. You can also measure a coil's resistance using a multimeter. Be sure to reference the manufacturer's specifications.

Get Started With Switches, Sensors, Solenoids and Relays

The intricate system of sensors, switches and senders in a vehicle can also wear out and fail. Most vehicles over a decade old use an ignition lock cylinder (where you insert the car's key on a steering column). This works with the ignition switch to start your vehicle. When the key is turned to a certain position, the ignition switch activates the electrical systems for ignition, as well as the various accessories like the radio. Like any other electrical component, the ignition switch can fail. If you notice your car stalls while driving, the accessories do not engage, or the key is difficult to turn, these could be symptoms of a bad ignition switch.

One of the most important sensors in your Chevrolet Impala is the oxygen sensor. It monitors the ratio of air to fuel in the engine. Oxygen levels in the engine can depend on the altitude, engine temperature, barometric pressure and the outdoor temperature. Symptoms of a bad oxygen sensor include rough idle, misfire, pinging (caused by slowed ignition timing), poor gas mileage and increased emissions. If too much fuel remains after combustion, the air-fuel mix is 'rich.' If there is not enough, it's called a 'lean' mix, and this can result in increased emissions.

Electrical and magnetic components are a crucial part of any vehicle's electrical system. Solenoids, like the starter solenoid or the VVT (Variable Valve Timing) solenoid, are small electromagnetic parts that generate a magnetic field through a coil wound tightly around a helix. Relays are electrical switches that convert smaller electrical currents to larger currents using electromagnetism. NAPA AUTO PARTS has a great selection of all sensors, relays, solenoids and switches big and small. Shop safely from the comfort of your home and get speedy delivery from NAPA AUTO PARTS.