A sudden stop on the road or uneven operation of the engine at idle often causes the owner of the car to panic, but the source of the problem can only be one small but critical element of the ignition system. Ignition coil It is responsible for converting low-voltage current from the battery into the high-voltage pulse needed to create a spark in the candles. If this component fails, the combustion process of the fuel-air mixture is disrupted, leading to power loss, increased fuel consumption and, in the worst case, complete engine failure.
Modern ignition systems, whether classical distribution or modern individual modules Coil-on-PlugThey require accurate diagnosis, as symptoms of malfunction are often masked as problems with the fuel system or oxygen sensors. A critical sign is the ignition pass in one or more cylinders, which is fixed by the engine control unit. Understanding the physics of the process and the ability to recognize the first βbellsβ will allow you to avoid expensive repair of the catalytic converter, which can collapse due to the ingress of unburned fuel.
In this article, we will discuss in detail how the car behaves when a faulty coil, what error codes should be searched for in the memory of the ECU and how to independently conduct an initial check without complex equipment. You donβt have to be a professional electrician to notice a clear deviation in the operation of the power unit. The main thing is to react in time to changes in the dynamics of acceleration and the nature of the exhaust sound.
The main symptoms of failure of the ignition coil
The first and most noticeable sign that cannot be ignored is the unstable operation of the engine, especially at low revs. The engine begins to "trot", that is, not work on all cylinders, which is felt as a strong vibration of the body and jerks when moving. Flame skips The MISfire creates a distinctive intermittent exhaust sound that an experienced driver will distinguish from normal operation even with his eyes closed. If you notice that the car twitches when accelerating, this is a sure signal that a spark of insufficient power or does not arrive at all enters the cylinders.
The second important symptom is a significant increase in fuel consumption. When ECU (engine control unit) fixes ignition gaps, it tries to compensate for the loss of power, enriching the fuel-air mixture. However, because the spark is weak or absent, the additional fuel is not completely burned, but is thrown into the exhaust system. This not only hits the ownerβs pocket, but also creates the risk of overheating and melting of the exhaust tract elements. The engine may stall at traffic lights or immediately after start-up, requiring a second starter attempt.
The third sign is the appearance of the smell of unburned gasoline from the exhaust pipe and the possible blackening of spark plugs. The coar on the electrodes indicates that combustion is inefficient. Also worth paying attention to the dynamics: the car stops "pulling" when overtaking, acceleration becomes sluggish, and the accelerator pedal loses its responsiveness. In some cases, when the coil body is damaged, you can hear the characteristic crackling of the electric discharge under the hood.
β οΈ Warning: Long-term operation of a car with a faulty ignition coil can lead to failure of the catalytic converter. Unburned fuel burns inside the catalyst, causing it to overheat and destroy cells, the replacement of which is much more expensive than a new coil.
A visual examination can also provide a lot of information. If cracks, chips or traces of plastic melting are visible on the coil body, the element requires immediate replacement. Often breakage occurs precisely through microcracks in isolation, especially in wet weather, when moisture enters the contacts. Ignoring these signs will lead to the fact that the machine may simply not start at the most inopportune moment.
Diagnosis with a multimeter and visual inspection
For accurate diagnosis of malfunction it is not enough to rely only on the sensations of driving, it is necessary to measure electrical parameters. Multimeter This is the main tool that will allow you to check the integrity of the coil windings. Before starting any work, be sure to turn off the battery's negative terminal to avoid short circuiting or damage to the vehicle's electronics. Remove the coil from the engine and clean it of dirt and oil to perform high-quality visual and instrumental control.
The test begins with the measurement of the resistance of the primary winding. Switch the multimeter to resistance measurement mode (Oms) to the limit of 200 Ohms. Connect the probes to the primary contacts (usually the central contact and one of the side or two side, depending on the design). Normal primary resistance values for most passenger cars range from 0.4 to 2.0 Ohms. If the instrument shows zero (short circuit) or infinity (cliff), the coil is faulty.
Then you should check the secondary winding, which creates a high voltage. Switch the multimeter to the limit of 20 kΞ©. One probe is connected to the central high-voltage exit (or contact leaving into the candle well), and the second to the contact of the primary winding. The resistance of the secondary winding is usually between 6 and 15 kOhms, although the exact values depend on the model of the car and the component manufacturer. A significant deviation from the norm indicates an interturn circuit or break.
βοΈ Checklist of primary diagnostics
Be sure to inspect the rubber tip (if any) and the spring contact inside the well. Often the problem lies not in the coil itself, but in the oxidized contact or broken-out tip insulator. The lobe and oil deposits can create conductive tracks that take the spark away from the engine mass. Also check the connection connector: the contacts inside the chips should not be oxidized or melted.
Analysis of OBD-II error codes and scanner operation
Modern cars are equipped with a developed self-diagnostic system, which records any deviations in the operation of the engine. When problems with the ignition coil appear on the dashboard, the lamp lights up. Check Engine. To obtain accurate information, you need to connect a diagnostic scanner or ELM327 adapter to the OBD-II connector. The scanner counts the fault codes stored in the ECU memory, which greatly simplifies the search for a problem cylinder.
The most common error codes that indicate coil problems start with the prefix P0300. This is a code that indicates accidental or multiple ignition failures. More specific codes, such as P0301, P0302, P0303, and P0304, indicate omissions in a particular cylinder (the cylinder number corresponds to the last digit of the code). If the scanner shows code P0351 or P0352, this directly indicates a faulty circuit of the ignition coil A or B, respectively.
It is important to distinguish between codes indicating electrical fault of the circuit and codes indicating ignition failures. Electrical codes (such as a circuit break or short circuit) are more likely to indicate a problem in the wiring or the ignition module itself. Pass codes can be caused not only by the coil, but also by candles, nozzles or low compression. Therefore, the P030X code requires further analysis: if you swapped the plug and coil between the cylinders and the error code moved along with them, then the defective element is found.
What are the pending error codes?
Pending codes are temporary errors that have not yet been confirmed enough times to turn on the Check Engine lamp. If the problem is reeling (periodic), the scanner can show the P030X pending code, which is an early warning of the onset of a malfunction, even if the lamp on the panel is not yet lit.
When using a professional scanner, you can also see the schedule of the cylinders in real time (Live Data). The "Misfire Count" option allows you to see which cylinder is failing right now, under load or idling. This is especially useful when the problem only manifests itself when the engine is warmed up or in wet weather, and is not always recorded as a permanent error.
Causes of frequent combustion of ignition coils
Ignition coils are quite reliable elements, but they are not eternal and often fail prematurely due to external factors. One of the main reasons is the condition spark-plug. If the gap on the electrodes of the candle is increased due to wear or the kalyl number is incorrectly selected, the resistance of the spark gap increases. The coil has to work in a strengthened mode, producing a higher voltage, which leads to overheating of the windings and breakdown of the insulation.
The second common cause is problems with the tightness of candle wells. In engines where the coils are installed directly into the well (coil-on-plug), oil leakage from the valve cover gasket is often found. Oil, getting on the coil body and in the candle well, destroys rubber elements, causes corrosion of contacts and creates conditions for thermal breakdown. Oil bath around the coil dramatically reduces the cooling efficiency and can lead to short circuits.
The third factor is the quality of electrical wiring and the state of the onboard network.