The 11 Least Reliable Engines in Modern Cars

When it comes to modern cars, not all engines are built to last. Some are plagued by design flaws, frequent breakdowns, and costly repairs, making them notoriously unreliable. In this article, we’ll take a closer look at 11 engines that have earned a reputation for causing headaches for drivers. Whether it’s excessive oil consumption or complete engine failure, these engines are ones to watch out for.

BMW N63 V8 (2008-Present)

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BMW’s N63 twin-turbocharged V8 engine delivered strong performance but at the cost of reliability. Common complaints include excessive oil consumption, overheating, and frequent timing chain failures. The engine’s complexity only added to the maintenance costs, making repairs both difficult and expensive. Owners were often frustrated by the high frequency of problems, and BMW had to address many of these issues through extended warranties. For many, this engine simply wasn’t worth the trouble.

Volkswagen/Audi 2.0 TFSI (2009-2015)

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Praised for its performance, the Volkswagen/Audi 2.0 TFSI engine suffered from significant reliability issues. Oil consumption was one of the main problems, leading to premature wear of the pistons and rings. Another common failure point was the timing chain tensioner, which caused extensive engine damage if left unchecked. Turbocharger failures were also reported frequently.

Subaru 2.5L Turbo (EJ255/EJ257)

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Subaru’s 2.5L turbocharged engines, often found in the WRX and STI models, were notorious for their reliability issues. Head gasket failures were common, leading to overheating and eventual engine damage. Owners also reported turbocharger problems and excessive oil consumption. These engines demanded vigilant maintenance, with any missed service potentially leading to expensive repairs.

Chrysler 2.7L V6 (1998-2010)

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Chrysler’s 2.7L V6 engine quickly developed a reputation for unreliability, mainly due to severe oil sludge buildup. The poor lubrication system often resulted in early engine failure. Other issues, such as timing chain problems and water pump failures, contributed to the engine’s notorious track record. Many owners experienced catastrophic failure before reaching 100,000 miles. With expensive repair bills, many vehicles were simply scrapped.

Toyota 3.0L V6 (1MZ-FE) (1994-2007)

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Although Toyota is known for building reliable cars, the 3.0L V6 (1MZ-FE) stands out as a rare misstep. This engine was plagued by oil sludge buildup due to poor ventilation, causing early engine wear and failure. Owners had to follow an aggressive maintenance schedule to avoid costly repairs. Many vehicles powered by this engine suffered from early breakdowns, which tarnished Toyota’s otherwise strong reliability reputation. Ultimately, the design flaws outweighed its otherwise decent performance.

Nissan 2.5L QR25DE (2002-2006)

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Nissan’s 2.5L QR25DE engine was notorious for a range of reliability issues. Excessive oil consumption, catalytic converter failure, and timing chain problems were frequently reported by owners. Catalytic converter debris was often sucked back into the engine, causing significant damage. The engine’s susceptibility to major failures at relatively low mileage made it a risky choice.

Jaguar AJ-V8 (1996-2000)

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Jaguar’s AJ-V8 engine, used in several luxury models, quickly became infamous for its reliability problems. Owners often experienced excessive oil consumption, timing chain tensioner failures, and engine knocking. The issues typically resulted in premature engine wear, with repairs costing thousands of dollars. The engine’s complexity made it difficult to maintain, further amplifying its unreliability.

BMW N47 Diesel Engine (2007-2015)

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BMW’s N47 diesel engine quickly became infamous for its timing chain failures. Positioned at the rear of the engine, the chain was difficult and expensive to repair, with failures often leading to catastrophic damage. Owners also reported excessive wear and noise issues. The engine’s problems were widespread, leading to a damaged reputation for BMW in the diesel market. Despite its efficiency, its poor reliability overshadowed its benefits.

Chrysler/Jeep 4.7L V8 (1999-2009)

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Chrysler’s 4.7L V8 engine, commonly used in Jeep and Dodge vehicles, suffered from multiple reliability issues. Head gasket failure, excessive oil consumption, and overheating were frequently reported. Additionally, timing chain issues often led to serious engine damage. Owners faced significant repair costs, and many engines failed prematurely. Despite its power, this engine became a liability for many Jeep and Dodge owners.

Mercedes-Benz M272/M273 (2004-2015)

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Mercedes-Benz’s M272 and M273 engines were plagued with balance shaft and timing gear failures, leading to costly repairs. Many owners experienced engine misfires, poor performance, and premature engine wear due to these defects. Despite being found in luxury models, these engines consistently failed to meet reliability expectations. The repairs were often prohibitively expensive, leaving many dissatisfied customers. Even Mercedes’ reputation for engineering excellence couldn’t overcome these flaws.

Toyota 2.4L 2AZ-FE (2002-2015)

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The Toyota 2.4L 2AZ-FE engine, used in models like the Camry and RAV4, suffered from excessive oil consumption, especially in high-mileage vehicles. Piston ring failure was the most common cause, leading to engine damage if not caught early. Despite Toyota’s reputation for durability, this engine faced numerous complaints. Repairs were costly, and some owners were forced to replace the engine entirely. It remains a rare blemish on Toyota’s reliability record.

This article originally appeared in MyCarMakesNoise.

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Author: Dave Johnston

Dave is a hands-on automotive technician with experience in performing service, diagnostics, and repairs on domestic and imported vehicles. He enjoys writing and sharing his knowledge far and wide.

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