After a few years on the market, each engine shows its true colors. And some of these colors are rather bleak when it comes to the seven units we have researched to make our list. The owners of many cars equipped with these engines have lots of grievances and complaints, so you should do your best to avoid buying them. This isn’t technically a Top 7 of sorts, as we would be hard pressed to figure out which one is actually worse than the other, so the order in which they are listed is purely arbitrary.
Audi/VW 1.8 T
The four-cylinder turbo unit has been widely used by the German automaker. You can find it equipping anything from the humble Skoda Octavia to the much more expensive Audi A6. No matter the car, the problem is always the same: sludge formation leads to huge repair bills.
This is mainly due to the fact that the owners tend to overlook the need to use synthetic oil, which is more expensive than the conventional one. Models from 1997 to 2004 are particularly prone to the issue.
Moreover, sludge formation isn’t the only issue, as coil pack failures are quite common. So is oil consumption.
BMW 2.0 diesel (N47/N47D20A)
Ah yes, the (in)famous N47 with its well-known and documented timing chain problem. Adding insult to injury, there is also the absurd positioning of the timing chain at the back of the engine. So in order to do any repairs, the mechanic has to take it out of the car.
Sure, you could say the idea behind this technical solution was that the timing chain was supposed to last the life of the car, but practice always beats theory.
To compound the problem, the N47 has equipped a wide range of vehicles made by BMW and Mini. You can find it under the hood of the BMW 1, 3 or 5-Series, as well as the X1, X3, and Mini, all built from 2007 to 2013.
The issue was so serious that back in 2013, BBC Watchdog featured it in one of their investigations. BMW has not made a comprehensive recall or acknowledged the problem outright.
Mazda 1.3 L Rotary Renesis
Mazda is renowned for its built quality, but there is a caveat. That caveat is the Mazda RX-8 and the main culprit is the Rotary-Wankel engine. This unit has been known as a troublesome one as apex seals can wear prematurely, resulting in lower compression. The fix is a total overhaul of the engine, at a very high cost.
If this wasn’t enough, the motor has a huge appetite for oil, and 2006 models are known to sustain damage to the catalytic converter due to oil migrating downstream.
VW 1.2 TSI petrol
The first 1.2 TSI engines are a real source of serious problems for the owners. This unit has been used by Skoda, VW, and even Audi, which means you can find it on a wide range of models. This has only made matters worse in terms of reputation for the German automaker.
The biggest issue with the 1.2 TSI petrol is that the timing chain is prone to failure. This can lead to catastrophic damage to the engine itself. The total repair cost can run up into the thousands of euros.
Toyota 3.0 petrol V6
The Japanese carmaker has a well-deserved reputation for reliability. Even the best sometimes make mistakes. One of these mistakes has taken the shape of a petrol engine. This power unit is very prone to clotting with oil sludge. Toyota blames the owners for not using the correct type of oil and also for not respecting servicing intervals.
However, there is more likely a defect in the breathing or circulation system of the engine. The affected models include V6 models of the 1997-2002 Toyota Camry, Avalon, Sienna, Highlander and Solara that were very popular in the United States and Asia. The Lexus ES300 and RX300 used the same problematic 3.0 L V6. After 2002, Toyota made some improvements that appeared to solve the problem.
Nissan 2.5 petrol four cylinder
Another Japanese brand with a reputation for quality that has made a serious design error. This time, the engine has a high probability complete destruction. Owners tell horrifying stories of the ceramic pre-catalytic converter built into the exhaust manifold disintegrating and ruining the engine.
It’s a big problem among 2002 and 2003 2.5 L four-cylinder Altimas, as well as Sentras with the same power unit. Altimas and Sentra SE-Rs equipped with the same engine built between January and May 2006 may experience unusually high oil consumption. This can lead to premature engine failure and possibly a fire.
Ford 4.6/5.4/6.8 petrol engine family
For the final entry, we have a whole family of engines, all with the same basic architecture. The modular design used with the big V8 Ford petrol motors is quite an example of bad design. We are talking about the units produced mainly from 1997 to 2007 and found on many Ford, Mercury, and Lincoln cars.
Owners have reported spark plugs blowing out of their engines and, in one instance, right through the hood. Imagine that!
Fortunately, Ford admitted that it had a problem and issued a Technical Service Bulletin with the number 07-15-2. Some engines produced between 2004 and 2008 from the same family have a unique spark plug design with a two-piece outer layer, that has been known to separate. The lower portion gets stuck in the engine leading to catastrophic failures and subsequent huge repair bills.