The modern car is a complex mechanism where every element of the ignition system plays a critical role. When the engine starts to triple, twitch or stall at idle, an experienced driver immediately suspects problems with the supply of sparks. Most often, the culprit of such symptoms becomes faulty-coilIt stopped giving tension to candles.
The problem is that most modern cars have one coil per cylinder, and it is impossible to determine visually which one failed. Errors on the dashboard can be deceptive or indicate ignition skips in general without naming a specific cylinder. That is why it is important to know the algorithm of actions for accurate diagnosis without visiting an expensive service center.
In this article, we will discuss effective ways to understand, Which ignition coil is not workingusing both simple methods "by ear" and accurate measurements with a multimeter. Understanding the principles of the system IGS (Ignition Coil System) It will save you time and money by bringing the car back to its previous dynamic.
The main signs of a coil failure
Before proceeding to an active diagnosis, it is necessary to fix the symptoms that appear during the operation of the vehicle. The first and most obvious sign is the unstable operation of the engine at idling. The motor can vibrate stronger than usual, and the revs begin to float, which is especially noticeable after warming up.
The second important symptom is a loss of power during acceleration. The car stops pulling, especially under load or when climbing uphill. It's because it's happening. fuel-air mixture In one or more cylinders, the combustion energy is not converted into mechanical motion.
⚠️ Warning: If you smell unburned gasoline from the exhaust pipe or see black smoke, stop driving immediately. The operation of the engine with ignition passes can quickly disable the catalytic converter, the replacement of which is very expensive.
It is also worth paying attention to increased fuel consumption. An electronic control unit (ECU) trying to compensate for the absence of combustion in the "dead" cylinder can enrich the mixture, which leads to overruns. Often, a lamp light is added to these symptoms. Check Engine It's on the instrument panel.
Diagnostics by Module Transition
The easiest and most affordable way to find out which ignition coil is not working does not require special equipment. This method, often referred to as the "exclusion method", is based on the sequential rearrangement of ignition modules between cylinders. It is effective if you use individual coils in your car.
The essence of the method is as follows: if an error indicates ignition gaps in the first cylinder, you change places the coil of the first cylinder with the coil of the second. After that, you need to start the engine and let it work for some time, so that the ECU recorded new data.
- 🔧 Remove the decorative plastic lining from the engine to access the candle wells.
- 🔌 Carefully disconnect the electrical connector and unscrew the suspect coil fastening bolt.
- 🔄 Install the checked coil in the neighboring cylinder, and replace the serviceable (conditionally) in its place.
- 📟 Consider errors with an OBD-II scanner or wait for the fault lamp to light up again.
If after permutation the error code shifted from the second cylinder to the first (or vice versa), then the problem is in the rearranged module. If the error remained on the previous cylinder, then the coil is good, and you should look for a reason in the spark-plug, nozzle or compression.
☑️ Permutation algorithm
Visual inspection and spark check
Although modern ignition systems are hidden from the eye, a visual inspection can give the first clues. Carefully examine the coil body for cracks, chips or traces of melting. Often break-in visible to the naked eye in the form of black tracks or dots on the body.
An assistant will be needed to check the spark. Unscrew the candle, connect it to the coil being checked and press the metal part to the "mass" (engine). When scrolling the starter should skip a powerful blue spark. If the spark is not present, or it is weak and red, the module needs to be replaced.
Pay special attention to the state of the rubber tip (candle cap). There shall be no trace of corrosion, moisture or white oxidation. The damaged sealer can leak moisture, which leads to short-circuit inside the well.
Why can the spark be weak?
A weak spark often indicates not only a malfunction of the coil, but also a low voltage in the onboard network, wear of high-voltage wires (if any) or a malfunction of the ECU. Also, the cause may be incorrectly exposed gap of the candle.
Multimeter coil check
The most accurate diagnostic method is the measurement of electrical resistance of the windings using a multimeter. This method allows you to quantify the condition of the node and compare the readings with the factory specifications. To perform the test, switch the device to resistance measurement mode (OM).
The resistance of the primary winding is first measured. The multimeter chips are connected to the contacts 1 and 2 (or central and lateral, depending on the model) on the coil connector. Normal values are usually in the range of 0.4 to 2.0 Ohms, however, the exact figures depend on the manufacturer.
The secondary winding is then checked. Here, the probes are connected to the central high-voltage exit and one of the contacts of the primary winding. The resistance here is much higher and can range from 5 to 15 kOhm. If the device shows infinity (break) or zero (closing), the part is faulty.
| Type of winding | Normal resistance | Sign of malfunction | Impact on work |
|---|---|---|---|
| Primary | 0.4 - 2.0 Ohm | Breakdown or KZ | Lack of spark |
| Secondary | 5000 - 15,000 ohms | Significant deviation | Weak spark, three. |
| Isolation. | Infinity | Break-through on the hull | Electric shock, EBU malfunction |
| Jack | 0 Ohm (contact) | Oxidation | Unstable contact |
⚠️ Warning: Never take resistance measurements on a warmed-up engine or immediately after it stops. Temperature affects the resistance of the metal, and the readings will be incorrect. Let the node cool to room temperature.
Use of oscilloscope and scanner
For professional diagnosis, a tester motor or an oscilloscope is used. These devices allow you to see the shape of the signal. ignition in real time. The oscillogram can determine not only the fact of the absence of a spark, but also the effectiveness of burning the mixture.
With the help of a diagnostic scanner, you can analyze the "Misfire Count" parameter. Start the engine and watch the readings in real time. Numbers rising in front of a particular cylinder will indicate a problem area.
It is also worth checking the power voltage on the coil connector. When ignition is turned on, one of the contacts should have a voltage equal to the battery voltage (about 12V). Lack of power may indicate a wiring break or a fuse failure, rather than the coil itself.
When buying a new coil, give preference to original parts or proven brands like Bosch, Denso or NGK. Cheap analogues often have a resource 3-4 times less than the original.
Replacement and prevention of the ignition system
If the diagnosis confirmed the failure of the module, it must be replaced. Remember that it is recommended to change the coils with a set or at least pairs on one side of the engine to ensure uniformity of work. However, if the budget is limited, a replacement of one element is acceptable.
When installing new parts, replace and spark-plate in this cylinder. The old candle could have been operating in an abnormal mode due to the faulty coil, and its condition could have deteriorated. It is also recommended to lubricate the inside of the rubber cap with a special dielectric lubricant.
Regular prevention will help to avoid sudden breakdowns. Check the state of the high-voltage cells every 30-40 thousand kilometers. Keep your candle wells clean: oil or antifreeze that gets there can quickly destroy the new coil.
Timely replacement of candles and the use of high-quality fuel prolong the life of ignition coils by 2-3 times.
Can I drive with a faulty ignition coil?
You can drive, but extremely undesirable and not for long. The engine will work unstable, fuel consumption will increase, and unburned fuel will burn out in the catalyst, destroying it. In addition, vibration is possible, which will damage the engine supports.
Why does the ignition coil burn?
The main reasons: overheating (disturbance of heat sink), moisture entering the candle well, the use of candles with the wrong gap (increases the load on the breakdown), as well as voltage surges in the onboard network due to a faulty generator.
What's the resource of the ignition coil?
The average life of modern individual coils is from 80 to 120 thousand kilometers. However, with aggressive driving, frequent short trips (the engine does not have time to warm up) and the use of bad gasoline, the service life can be reduced to 40-50 thousand km.
Does the quality of gasoline affect the coils?
Yes, indirectly. Bad gasoline causes detonation and a change in the combustion rate of the mixture, which changes the load on the ignition system. In addition, poor-quality fuel can lead to the formation of soot on candles, increasing resistance and requiring a higher voltage for breakdown.