How to Diagnose Problems with Your Car

Cars are finicky things, made up of what seems like a million parts that work seamlessly together only thanks to some sort of forbidden voodoo magic. If your car starts acting up, it’s easy to feel helpless. After all, it seems like a trip to the mechanic is inevitable – and that usually costs big money regardless of the outcome.

But what if you could diagnose your car yourself? It might seem like an intimidating task for anyone who doesn’t consider themselves a mechanic or a gearhead. But with a little bit of logical deduction, figuring out what might be wrong with your car may not be as hard as you anticipated. There’s plenty of repairs that you can likely pinpoint from just noticing the right symptoms.

So what are the secrets to knowing your car a little better? Let’s dive into it.

How to Diagnose Car Trouble: Where to Start

Diagnose the engine

Image courtesy of Pixabay

Car trouble is an intentionally vague term – it encompasses anything that might go wrong with your car. That includes the four major systems comprising the modern automobile: the engine, the suspension, the brakes, and the transmission. These four components – largely tied together by the automotive computer system – are the basic foundation of your car. They enable your car to comfortably go, turn, and stop.

If you can narrow down your car’s ailment to one of these three categories, you’re already on the right track. That step alone sets you up to methodically listen, observe, test, and uncover what exactly might be going wrong.

Within each of the aforementioned subcategories are some telltale symptoms for common mechanical issues and failures.

Engine

The engine is the beating heart of your car. In its most basic sense, the engine compresses and ignites the gas/air mixture to create combustion, which it then turns into mechanical energy. That energy is routed through the transmission to the driven wheels, thereby moving your car.

Common issues related to your engine include poor performance – think a rough idle and sudden inadequate passing power – stalling, overheating, and starting trouble. Many of these issues, however, are fairly easy to pinpoint at home. Take poor performance, for instance. When was the last time the spark plugs were changed? Often times, a simple tune up with new plugs and wires can wake up an engine that bogs down or idles rough. On that note, be sure to pinpoint exactly when your car is acting up. Let’s take the bad idle as an example. Does it only idle rough when cold, or also when the engine is warm? Or does it happen every time you start the car?

The first step to understanding why your engine isn’t running smoothly is to understand the circumstances in which it acts up. Once you pin down the precise symptoms, you can begin to use the internet, repair manuals, or knowledgeable friends to logically hypothesize what could be wrong. The more thoroughly you understand the problem, the quicker and easier it will be to find an answer.

Suspension

Your suspension is everything hiding under your car that keeps the ride smooth even when the road gets rough. Springs, control arms, tie rods, bushings, and other parts make up what we collectively call the suspension.

When these parts fail, the results are pretty obvious. The ride typically gets flinty; bumps and imperfections are no longer filtered out with nearly the same sophistication as before. Trouble may also be audible: clunks, thunks, and squeaks can commonly be heard with something on the suspension gives out.

Again, take the scientific approach. First off, where is the sound coming from? What does it sound like? When does it happen? If it isn’t a sound but a ride quality issue, try to feel if the trouble is coming from the front or rear. You might notice the steering wheel is constantly pulling to one side. You might notice the wheel binds if turned in one direction. You might feel the rear end slam and crash over every bump.

All of these annoyances are symptoms of bigger issues. Start with these symptoms and trace them back to the root cause.

Brakes

We’ve said it before – brakes are about as critical as it gets. You need a quality pair of stoppers because using someone else’s bumper is not the way to slow down. And when brakes begin to go, you need to diagnose the issue and react promptly.

Brakes are considered wear items, so periodically you’ll need to replace your pads and rotors.1 There’s also the vacuum booster, the lines, and the master cylinder, but these parts are less likely to go. When they do, you’ll notice severely impaired stopping power, a soft brake pedal, and potentially the brake warning light illuminating on the dashboard.

Pads and rotors, however, will wear out – and you need to know how to tell when they go. Rotors may warp; when they do, you’ll feel the brake pedal pulsating with every stop. Pads wear down over time, and at the end of their life they’ll begin to squeal loudly each time you apply the brakes.

With brakes, it’s all about pedal feel and what you hear. Keep an eye out for a funky-feeling brake pedal or unpleasant, shrill squeals – both classic signs that you’re due for brake work. If you determine your brakes are at fault, consider recycling them with your mechanic.2

Transmission

The transmission enables you to drive both fast and slow by the magic of torque multiplication. We won’t get bogged down by the specifics, leaving you instead to imagine swapping gears on a bicycle. Know how the numerically lower gears enable quicker acceleration but lower top speeds, while the higher gears result in the opposite? Automotive transmissions are the same concept.

Transmissions are pretty apparent when they start conking out. How do the shifts feel – firm, sloppy, delayed? Does the gearbox not want to downshift even when you accelerate? Do you smell something burning after engine braking or hauling up a hill? All these symptoms are likely due to a transmission fault.

A word of caution: if you feel your transmission is failing, bring it to experts for service. Modern automatic gearboxes are very complex, to say the least. Even if you can determine the issue – and we say good luck with that – there are slim odds you’ll have the tools or expertise to properly do the jobs.

What Tools Can I Use to Diagnose My Car?

Car diagnosis tools

Image courtesy of Pixabay

There are a few excellent tools on the market for diagnosing your car. Our favorites? Far and away, an OBDII reader and a battery charger. We’ve discussed both in previous articles, but it bears repeating why we can’t recommend them enough. These two tools are enough to determine many common componentry failures right in your driveway.

OBDII Readers

These devices (an acronym for onboard diagnostics, generation II) are lifesavers when your check engine light comes on. Typically, the check engine light appears with no warning – and no noticeable symptoms. But plugging in an OBDII reader into the special port in your car will enable you to extract any fault codes being thrown by your car’s ECU.

Once deciphered, those codes will point exactly where your failure is. It might go so far as to tell you to want the exact part to replace, but it will put you in a very workable ballpark. It may even empower you to try handling the repair yourself as well.

We can’t say enough about a quality OBDII reader. If you’re interested in purchasing one, check out our article on the best readers on the market.

Battery Chargers: Battery chargers are another lifesaver. These compact little devices can quickly – or slowly, your choice – juice up your dead car battery. They can save you in a pinch or help maintain a small battery charge over the course of winter storage.

Battery chargers are straightforward: they plug into the wall and turn your 120V alternating home current into 12V direct current, which is the stuff your car battery likes. You’ll be reaching for your battery charger if you turn the key only to hear a click. Without a charge, your car won’t start – and a battery charger is the best way to get back on the road.

On the same note, a battery voltage tester is another tool to keep in your arsenal. Voltage testers can measure the strength of your battery, which is a great thing to check before heading into winter or taking a long road trip in a car with an old battery. Batteries typically need to be replaced every four to six years, and a voltage tester is an easy, fast way to check how far off you are from needing a new battery.

Parting Thoughts

Diagnosing car trouble is all about methodically isolating and analyzing symptoms. Determine what the symptom is, where it is coming from, and when it occurs. The answers you get will make further research that much easier than throwing a broad, generic question into the maw of Google. Or, in this day and age, you could also just use an app. 3

And we’ll say it one more time: an OBDII reader, battery tester, and battery charger are some of the best things you can keep at home to make your automotive diagnosis and repair that much easier.

With the right tools and know-how, the next time your car acts up, you can confidently begin the diagnosis process at home, saving money on initial visits to mechanics and arming yourself with knowledge before you ever step foot in a repair shop. With the tips outlined above, you’ll have no issue getting to the bottom of your car trouble.

Article Sources

Ride Digest uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.

  1. How Long Can You Drive With Bad Brake Rotors? Brakeexperts.com Updated 2021. Accessed 23 Sept 2021.
  2. Lyu Y, Ma J, Åström AH, Wahlström J, Olofsson U. Recycling of worn out brake pads ‒ impact on tribology and environmentSci Rep. 2020;10(1):8369. Published 2020 May 20. doi:10.1038/s41598-020-65265-w
  3. Matchar, Emily. This App Can Diagnose Your Car Trouble. smithsonianmag.com. Published 5 Dec 2017. Accessed 27 Sept 2021.