Car jerking: when your engine warns you that something is wrong

Whatever vehicle we own, it's almost certain that sooner or later we'll end up at the mechanic's. Whether it's for a routine check-up or due to a breakdown. And it's precisely these breakdowns that can cost us the most time and money.

Some breakdowns happen unexpectedly, while others give you warning signs beforehand. One of these warnings that a breakdown is imminent is jerking. If your vehicle jerks when you start or accelerate, it could be a sign that something isn't working as it should and that it's time to take it to the mechanic to avoid bigger problems.

Why does my car's engine jerk?

Regardless of the wide variety of possible problems, their origins can generally be grouped into certain areas: dirt, electrical faults, and mechanical failures.

Dirt, the Greatly Forgotten Factor

It only takes a buildup of more dirt than necessary on any part of the combustion system for the process to stop functioning optimally. However, certain parts, due to their importance, can cause a significant loss of power and, consequently, increased fuel consumption when they become excessively dirty.

- Injectors: Like any other part of our vehicle, injectors wear down and accumulate dirt over time. This dirt is usually a product of fuel residue that the fuel filter cannot filter out. If the problem is minor, we will notice slight jerking when starting and accelerating; otherwise, the injector may stop working, and with it, the cylinder it feeds. This results in a loss of power, or in cases of extreme blockage, the vehicle may not start at all.

- Fuel Filter: As mentioned above, the fuel filter is a protective mesh that prevents impurities and fuel residue from reaching the vehicle's injection system, fuel pump, fuel supply circuit, or injectors. Regular replacement is sufficient to prevent more serious problems.

- Diesel Particulate Filter: The diesel particulate filter (DPF) is responsible for trapping polluting particles produced by combustion before they are released into the atmosphere. Within its porous walls, it retains solid particles from the exhaust gases, releasing them—after treatment—during the regeneration process. This significantly reduces the level of pollution.

This regeneration process is carried out automatically and, in addition to treating the particles stored within its walls to reduce their polluting effects, it is also responsible for cleaning the particulate filter.

What often happens is that this regeneration process doesn't take place, and the particulate filter becomes so clogged that it acts like a plug in the exhaust pipe. As a result, the vehicle loses power, and other components such as the injectors, turbocharger, EGR valves, and intake manifolds are negatively affected.

Mechanical Failures: The Most Common

When a vehicle jerks, and these usually originate from mechanical failures, these faults are generally located in the following areas:

- Gearbox: Excessive mileage or a lack of proper maintenance are usually the main causes of malfunctions in manual gearboxes.

- Throttle Cable: Of all the faults mentioned in this article, this is the least harmful. While it may initially seem just as serious as the other issues, it's usually resolved by replacing the cable, and presents no greater danger than the discomfort of feeling those 'jerks' your vehicle experiences when starting or accelerating.

Electrical faults, the most troublesome

In our opinion, these are the most annoying. They don't usually give any warning, and can range from something as simple as a broken wire to a faulty ignition coil or the ECU.

- Ignition coil failure: The ignition coil deteriorates primarily due to driving at high RPMs. In cars with more than one coil, if one fails, the vehicle will sputter and run. However, if it only has one coil, it simply won't start.

- Faulty ECU: The ECU, or control unit, is responsible for controlling the proper functioning of your vehicle, managing fuel injection, ignition, and gear selection. It also controls other vital systems such as ABS, central locking, and ESP. Therefore, a faulty ECU can lead to malfunctions in any of the aforementioned systems, and Of course, this can cause you to feel those annoying jolts both when starting and when accelerating.