The internal combustion engine may be nearing its final days, but all the R&D and effort from various car and parts manufacturers in recent years has meant it’s become more powerful, requires less fuel, and is eco-conscious. Cars now put out unthinkable power figures just a few years ago, while being downsized in displacement, and lasting longer even under the burdens of high pressure and working temperatures that make all that possible.

Much of that new-found power is due to engine efficiency and advancements in ignition systems. Manufacturers have moved away from traditional distributor-based systems to more advanced coil packs and coil-on-plug ignition coils that deliver much higher voltages, improved combustion, lower energy use, fewer parts, carefree driving, and lower maintenance needs. This facilitates the use of performance plugs to get the most out of the ignited air and fuel mixture.

Accompanying systems and sensors monitor exhaust gas temperatures, unburnt oxygen levels, and the position of the cam and crank as combustion takes place. This is overseen by the car’s ECU to allow for smooth operation.

Common Indicators of a Failed Ignition System

While newer cars fitted with a ‘distributor’ engine ignition coil do see fewer issues. No car is immune to electrical problems. These generally emanate from the coil packs and the plugs or are signs that related sensors have seen better days. Typical indicators of a failed system include:

Loss of engine power – Any problems with the ignition system mean a loss of engine power, due to voltage that’s not delivered to plugs to ignite the air and fuel mixture. This can be from worn or fouled spark plugs, fraying in spark plug wires, or damage to coils and coil packs requiring you to buy a new engine ignition coil.

Stalling and hard starts – The role of the ignition is to provide the right voltage at the right time so combustion occurs. Malfunctioning coils or faulty plugs mean this doesn’t happen, and results in difficulty turning the engine over, or repeated stalling. Related issues are unburnt fuel that clogs the exhaust and catalytic converter.

Changes in engine noise – clicking sounds and the engine not starting point to a failed starter motor (or depleted battery). In addition, misfires or failed combustion in any cylinder lead to the engine coughing or sputtering and are accompanied by pronounced vibrations due to bad ignition timing. Backfiring or the fuel combustion outside the cylinders (most often in the exhaust), is a loud and unnerving sound that also points to faults in either the plugs or the coil.

Rough idling – this is a related issue of missed ignition timing that doesn’t correspond to engine speeds and fuelling. You’ll notice vibrations as RPMs repeatedly rise and fall. And when sudden jolts when pressing the gas pedal.

Poor fuel economy – if all parts are working as they should, then sparks happen at the right time and ignite the designated amount of fuel for the engine load. With faulty ignition components, drivers may notice a substantial increase in fuel use, This is down to low voltage in the coils, soiled or damaged plugs, and the ECU overcompensating by spurting more fuel from the injectors.

During any of the problems above, drivers will also see the ‘check engine’ light in the dash. When running a diagnostics test with the car connected to an OBDII scanner or computer, most cases point to damaged coil packs or plugs.

Issues can also arise due to bad sensors, most notably the oxygen sensor, and the camshaft and crankshaft position sensors. Though rare, newer vehicles can experience problems with the ignition module, or the electronics controlling the ignition, and separate from the ECU.

Coil Pack Issues

Most manufacturers today don’t consider an engine ignition coil as a regular replacement part. There are vehicles with 200 thousand plus miles on the odometer, and no signs of ignition failure, or any of the symptoms stated above. Not all coils are created equal though, and not all drivers are that lucky.

Newer ignition coil types do tend to be more durable even while providing almost double the voltage than older conventional distributor types to feed power-hungry spark plugs. Coil blocks, pencil coils, and rail systems fall into this category. They’re typically more efficient too, with no voltage lost in plug wires.

The downside to this is that once the coil goes bad, you’ll be replacing the whole part, or in the case of rail systems, the whole rail. While the job is relatively straightforward and completed within minutes, car owners do have to dig deep to get replacements. Prices vary for different engines and from different makers but are generally higher the bigger (higher cylinder count) and more powerful the engine is.

The good news for older cars with distributor coils is that parts are significantly cheaper, and only the faulty parts, either the distributors, the distributor cap, housing, or rotor, and (one or all) plug leads need to be changed. The downside is that you’ll be doing this more often, as older ignition systems lose puff around the 30-thousand-mile mark.

Spark Plug Issues

Plugs, unlike coil packs, need to be replaced at recommended intervals. After all, they provide the spark needed for combustion. Here lifespans differ according to the plug type. The cheapest, basic copper and nickel plugs should give you 30 thousand miles of worry-free motoring. Platinum variants last around 50, and the priciest Iridium spark plugs are good for roughly 75 thousand miles.

Common problems are worn electrodes due to overheating, improper electrode gaps (meaning uneven sparks or misfires), and cracked or damaged insulation housings. Contamination from oil (often from blown gaskets or worn piston rings) or the electrodes collecting unburnt fuel and soot (carbonization) are other frequent reasons why they fail prematurely. Plugs will also malfunction due to faulty coil packs supplying too high voltage.

Issues with Sensors
Ignition timing in newer engines is made easier with sensors. The crank position sensor for instance determines the speed and position of the crankshaft so that coils and plugs can fire at the correct time. A faulty sensor often leads to stalling and hard starts. Damaged or disconnected wiring is often the cause, but there can also be problems with the internal sensor circuitry, damage to the plastic housing because of excessive engine heat, and misaligned parts (wheel and pins) by which the sensor gauges the crank position.

The camshaft position sensor also has a say in the engine running smoothly, particularly the ignition system. This part determines the position of the inlet and outlet valves in relation to the crankshaft and pistons, so helps the ECU with correct timing and the firing sequence in the cylinders. Cam position sensors fail because of cracks in the outer housing, exposure to moisture or dirt, more severe mechanical damage, or faulty wiring and connectors. This leads to misfires, and stalling, and eventually, the car won’t start.

Troubleshooting Defective Ignition System Parts
While replacement parts are the easiest way out, most issues can be revealed with a simple diagnostics test. Scanners with current software will generally point to the cylinder where misfires (or non-starts) occur, meaning either bad plugs, defective coils, or wiring problems. Remove the spark plugs from wires or the coil-on-plug connectors, remove the plugs with a socket, and do a thorough inspection. Plugs with cracked or damaged insulation casings need to be replaced.

Those that have oil or carbon buildup can be cleaned using medium grit sandpaper or a wire brush. Once cleaned, check the gap between electrodes with a gap tool. Plugs should also be tested with a spark plug testing tool. This connects to the ignition wire on one end and the plug on the other, with the engine on and observing whether there’s a visible spark. Lastly, check the wiring for plugs that connect them to coils as these are often the first to cause ignition issues if damaged, frayed, or affected by environmental factors, such as moisture.

Coils and coil packs are generally tested with a multimeter and the resistance results are compared to manufacturers’ recommendations (usually between 0.3 and 1 ohm). Distributors, distributor caps, and rotors are first checked for visible damage, and then a multimeter is used to verify that resistance is up to scratch. The same tool can be used to diagnose ignition modules.
Lastly, sensors are checked for rust, debris, loose wiring, or burned and broken connectors. Sensors will display code readouts during diagnostic scans and a multimeter can verify if they are in working order.