What are the symptoms of a faulty ignition coil in an old Jetta?
4 Answers
There are three main symptoms of ignition coil failure: short circuit, open circuit, or grounding of the ignition coil winding; surface discharge; and insulation aging. Here is a related introduction about the igniter: 1. Composition: The igniter is mainly composed of a power source, ignition coil, distributor, ignition switch, spark plug, additional resistor and its short-circuit device, high and low voltage wires, etc. 2. Identification method: When all the wiring of the igniter is connected, do not connect the power line (the charging end of the AC igniter) first, or disconnect the high-voltage output line of the magneto in advance. After ensuring that the ground wire of the igniter is well connected to the ground wire of the vehicle circuit, pull the high-voltage cap out of the spark plug and insert a spare spark plug to ground it on the vehicle body. Finally, connect the DC circuit of the motorcycle (the live wire is connected to the positive terminal of the battery) to the charging end of the igniter.
My neighbor who used to drive an old Jetta always said that a faulty ignition coil is really annoying! You can clearly feel the engine losing power when driving, and even pressing the accelerator pedal all the way won't increase the speed. The most obvious symptom is the car shaking jerkily, like riding a horse, especially at idle when the whole vehicle trembles, and the exhaust pipe makes a sputtering sound. Fuel consumption also skyrockets, and the engine check light usually turns yellow. If left unrepaired for a long time, it can even damage the catalytic converter. The electrical circuits in these old cars are particularly afraid of moisture, so the probability of failure is higher on rainy days, and sudden stalling is also common.
I often hear old Jetta owners complaining about this issue. The ignition coil is failing, causing the idle to shake violently like sifting flour, and the exhaust pipe sound becomes intermittent. The throttle response is sluggish, making it difficult to climb hills. The most troublesome part is that it tends to misfire or stall on rainy days or after washing the car—suddenly jerking a couple of times before shutting off. Pulling out the spark plug to check the spark reveals that the problematic cylinder either has a weak red spark or no spark at all. Replacing it early can save some fuel costs; otherwise, an extra two liters per 100 kilometers is quite common.
The most dreaded issue with old Jettas is the ignition coil acting up. The engine wheezes like a bellows, and the exhaust pipe makes popping sounds like flatulence. Starting the car isn't a problem, but the tachometer needle dances up and down, and driving feels like stepping on cotton with no power. Sometimes, during sudden acceleration, it jerks forward as if being pulled back. If one of the four cylinders fails, the steering wheel vibrates so much it numbs your hands. The old Jetta's ignition coil has poor heat dissipation, making it particularly prone to failure in summer traffic jams.
