Is It Dangerous to Buy a Car with Aftermarket Parts Installed?

It's not always possible or practical to buy or lease a new car. Sometimes, you're faced with having to purchase a used automobile. While this process may seem straightforward, searching for the right used car is a lot different from picking a new one off of the lot. There is one critical thing to consider when looking into a used automobile, and being aware of this prior to purchase could save you a lot of time and headaches in the future.

Is it dangerous to buy a car with aftermarket parts installed?

The answer is yes, in some cases it can be dangerous to purchase a vehicle with aftermarket parts installed by a previous owner or unqualified shop. However, there is a fine line between cars modified in a safe way and ones that are modified in an unprofessional or illegal manner. Some parts can increase the value of the vehicle to the right buyer, and others can lead to trouble and reliability issues later on. This is why it is good to be informed about aftermarket parts and modification.

Here are a few aftermarket parts commonly installed on used vehicles to gain fuel economy and horsepower, yet may interfere with emissions laws or reliability of the vehicle:

  • Cold air intakes: These are commonly installed due to an advertised increase in fuel economy and slight increase in horsepower. Cold air intakes are unnoticeable by the average driver. One upside is that many replace the factory filter with a re-washable and reusable lifetime filter. They can let in more dust than factory filters and in some cases, cause a check engine light or failed emissions test due to improper installation of the mass airflow sensor.

  • Performance mufflers/Exhaust systems: These are advertised to increase horsepower and give the vehicle a more aggressive sound. It is good to know whether a sound changing muffler has been installed or if the entire exhaust system has been replaced with a reliable and state emission legal brand. If the exhaust system or muffler is missing emissions equipment such as the oxygen sensor or catalytic converter, the vehicle may be unsafe to drive and may not pass emission testing. Always check the installation receipts for a reputable brand and reputable shop. If the paperwork is not available, have a trusted mechanic take a look.

  • Supercharger/Turbochargers: Anytime a vehicle is equipped with a non-factory forced induction setup, there should be paperwork and/or a warranty provided by the owner to ensure the work was performed by a reputable source. Great caution should be taken with cars that have these hefty modifications, as they can be very powerful and safety equipment may need to be upgraded. Often, vehicles with these modifications are not street legal. Unless you are searching for a race car, stray from cars with these parts.

  • Aftermarket blow-off valves/intercoolers/gauges/shifters: On cars that come equipped with factory turbochargers, owners may have installed aftermarket turbo blow-off valves, boost gauges, or shifters. These aftermarket parts, if of good quality, can better the driving experience for some, and give the car a more crisp and responsive driving experience if installed properly.

  • Wheels/tires/suspension parts: A good set of wheels and a lower stance can make a car look great when done properly, but be prepared to spend more on tires and suspension parts over the course of ownership if the vehicle has a modified wheel alignment, or excess camber. Being low can also damage exhaust, crack front bumpers, and puncture necessary engine components such as the oil pan.

Keep in mind that while this short list of aftermarket parts and modification reveals the good and the bad of each common aftermarket part, it is up to you as the buyer to have a mechanic look at any parts you are unsure of. While having a nice set of wheels and aggressive exhaust may increase the value to the right buyer, in many cases the trade in value decreases significantly. This is because the general attitude is that unmodified vehicles are more valuable. Always be aware that aftermarket parts can be illegal, and can be very dangerous if tampering with the emission system has occurred.

When looking at a vehicle, there may be clues that the vehicle has had aftermarket modifications. These clues include:

  • A louder than normal muffler
  • A cone-shaped air filter
  • A suspension that looks altered
  • Mismatched paint, such as near a spoiler or bumper
  • A different steering wheel

Many aftermarket parts can improve the car’s performance, but it’s important that buyers are aware of those modifications, and that they were installed correctly. If you suspect that your car has had aftermarket modifications, a pre-purchase inspection can help make sure that everything is in proper working order.


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Caz

17 years of experience
57 reviews
Caz
17 years of experience
Honda Insight - Pre-purchase Car Inspection - Acworth, Georgia
Patient, thorough, professional and takes his time to explain things. This is the second time I have used Caz's services, and he consistently delivers. Look forward to working with him again.
Volvo XC90 - Pre-purchase Car Inspection - Alpharetta, Georgia
My husband and I are looking for a reliable used car for our teenage drivers. We had two that we were considering and wanted to have them inspected prior to purchasing. Caz did a thorough inspection of both vehicles and recommended we walk away from both. We really appreciated his transparency and knowledge. We will definitely use Caz again.

Chris

22 years of experience
2001 reviews
Chris
22 years of experience
Porsche Macan - Pre-purchase Car Inspection - Irvine, California
Chris you as so knowledgeable and really out my mid at ease with the private seller purchase. Highly recommend to anyone shopping for a car :)
Lexus ES300h - Pre-purchase Car Inspection - Temecula, California
Amazing guy.... called and gave me what felt to be his honest and straightforward opinion on my vehicle.... def will book him again in the future for work

Casey

19 years of experience
27 reviews
Casey
19 years of experience
Hyundai Santa Fe - Pre-purchase Car Inspection - Katy, Texas
Casey is awesome. Helped me fully understand the health of the used vehicle I was buying for my mother in law. Great service and very knowledgeable for sure. Casey found only one issue we needed to deal with and was able to book the repair just a few days later.

Colby

14 years of experience
21 reviews
Colby
14 years of experience
Ford Ranger - Pre-purchase Car Inspection - Longmont, Colorado
Colby called to notify me he was in route to the inspection--to ease my mind and to ask if there was anything in particular/extra I wanted him to check out. He was going to do a pre-purchase inspection of a 2002 Ford Ranger. He assured me that I hired the right guy since he'd worked for Ford for 13 years. An hour or so later, he called me while he was driving home to discuss his inspection. I could ask him everything I wanted as we dialogued. That was so helpful! And way more personable and real than just reading the report he emailed. The report was thorough and included a test drive. He had recommendations for some work to be immediately done; rotors & brake pads. Then, included the cost for him to do that work should I choose. The price was fair and not crazy expensive. I'm still deliberating on whether to have that done or to wait for my mechanic to do it once I have the truck. Thank you again Colby.

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