Ford has a diverse portfolio of products, engines included. From tiny EcoBoosts to the massive Power Stroke diesels in Super Duty models, Ford has covered a lot of real estate in terms of engine development — and that means there’s also plenty of room for things to go wrong. While modern engines like the Coyote V8 and 7.3L Power Stroke are generally quite reliable, even this venerable company has had its hiccups over the years — and quite a few of them, in fact, ranging from poor design choices to defective parts.

It’s not surprising for such a long-lived brand to have some major flops over the years, be it the infamous Ford Pinto or the dismal publicity of the Edsel brand. Generally, though, Ford’s engines aren’t the highlight of the show. Sometimes, though, a car’s engine is so bad that it elevates even good-quality vehicles to the Hall of Shame. These are the ones we’ll focus on — engines that are so bad that they effectively defined the cars they were in.

In this article, we’ll look at several recent Ford engines that are either fundamentally flawed or have been so unreliable that they actively discourage consumers from purchasing vehicles with them. To keep things somewhat fair, we’ll stick to modern engines used for their intended purpose, comparing them to other engines in their class. Let’s open up the hood and have a look.

These Ford EcoBoosts, comparatively speaking, aren’t too bad, with no outstanding recalls and relatively few customer complaints — save for one key feature, that is: the timing belt. These EcoBoosts have timing belts submerged in engine oil, which shouldn’t be an issue if owners maintain their engines properly. But according to mechanics and owners alike, even following Ford’s maintenance intervals to the letter might not be enough because of the way the timing belt interacts with the engine oil.

To better understand the problem, we must look at the timing belt itself and why it’s submerged. A timing belt is designed to synchronize the top and bottom halves of an engine; it’s a relatively harsh working environment, with components typically being either polyurethane belts, chains, or gears for high-load applications. The belt has certain advantages — it’s quieter and more compact, for instance. So what if you could make it even quieter by just submerging it in oil? Therein lies the problem — the oil can accelerate belt wear, and it’ll carry residual bits of belt to other components.

In other words, the belt tends to shed rubber, which can then clog up key junctions such as the oil pump and turbocharger. Mechanics and owners also complain about the time and effort required to diagnose and replace these belts — making it a costly task. On top of that, some of these engines were also recalled for faulty oil pumps, adding to the long list of potential failure points caused by this design.

The 5.4-liter Triton V8, specifically in the three-valve configuration, is more or less the ugly duckling of the Triton engine family. This powerplant is one of Ford’s most problematic, with the most major issue being a poorly-designed timing system. The problem here is that the timing tends to “jump,”  meaning the belt will slip off for a split second, leading to engine components such as the valves and pistons moving out of sync. 

Compounding this issue is that the Triton is an interference engine, meaning the valvetrain and pistons operate in the same space inside the engine. If such an engine is out of sync, the valves may be open when the piston reaches the top of its travel, and the two will collide, ruining the valvetrain and/or piston assembly. These engines must have robust timing mechanisms to avoid catastrophic damage — which the Triton doesn’t have.

The 5.4-liter Triton has other problems besides the timing issues; for one, the spark plug design damages plugs when attempting to remove them, according to owners. Owners also report that the engine tends to misfire, while there are occasional complaints of fuel delivery issues dating back to when these engines were still in production. There have been many better engines developed since the 3V Triton’s days, making it a lackluster product by comparison — especially considering the potential maintenance headaches.

Likely the most versatile engine on this list by a long shot, this V6 was available in many Fords over the course of three generations: Ford F-series trucks, police cruisers, Mustangs, and the venerable second-gen Ford GT. It’s a modular engine in every sense of the word, available in different configurations to fulfill different roles. Not all 3.5s are created equal, and many of the second-gen models in particular suffered from something vicious: cam phaser issues resulting in a horrific rattling sound.

The 3.5L engine has variable valve timing, where the camshaft self-adjusts to optimize the valvetrain for better efficiency or power delivery as needed. The cam phasers’ job is to direct the cams to open or close, and defective phasers mean the engine may not lock in the timing right away, leading to that rattle. According to owners and mechanics, this problem can lead to worn timing components and damaged cam phasers, which can then result in more serious issues ranging from rough idling and inconsistent power delivery to strain on the timing chain. Owners can allegedly mitigate this problem by holding down the gas pedal for a few seconds while turning on the ignition. This builds up oil pressure in the cam phasers before startup, thus preventing the rattle.

Aside from the cam phasers, periodicals, owners, and enthusiasts also report several other sources of headaches, including carbon buildup, intake vacuum pump failure, and timing chain failures (likely related to the phasers) on the bottom end. Luckily, these only affect a relatively small subset of 3.5s, with the problem being resolved for the third-gen that debuted in 2021.

The 6.0-liter Power Stroke has rightfully earned its place as one of the worst diesel engines ever, thanks to a range of issues, ranging from EGR cooler failure, blown head gaskets and head bolts, oil system leaks, and various electrical gremlins related to the fuel injection control module. The sad part is, underneath all this disaster lies a relatively robust design, at least according to (frustrated) mechanics and owners who need to perform various preventative measures to keep these engines from an early grave.

Many of these issues presented themselves early in the engine’s life, with contemporary reviews and owners expressing concerns about EGR cooler failure within as little as five years, for example. The head gaskets proved equally troublesome, with underperforming gaskets resulting in coolant system leaks. Other issues, such as wear on the pushrods caused by undersized guide holes in the head gasket, have also been reported, as well as stretched and sheared head bolts. These issues cropped up as early as the mid-2000s for some unlucky customers.

While the list of issues plaguing this engine is quite daunting, they’re all well-known and generally resolved by this point. They typically stemmed from the tighter emissions standards these engines had to meet compared to the outgoing 7.3-liter, and many of these changes can be reversed or otherwise upgraded to make a reliable engine. But for a stock 6.0L, it’s most certainly a buyer-beware situation.

It’s not uncommon for new engines to have teething issues. Take the 6.0-liter Power Stroke, for instance, which was a noticeable downgrade from the 7.3-liter. One might assume, then, that Ford would have learned its lessons when it came time to replace the 6.0-liter. On the one hand, it did: the heads are no longer spontaneously disassembling themselves from inadequate head bolts, for example. However, Ford introduced a new host of problems with the next-generation 6.4L.

The new issues found in 6.4-liter Power Stroke diesels include everything from leaking radiators caused by inadequate materials to cracked pistons. The latter is not uncommon on high-mileage engines, but that’s not the case with the 6.4-liter, and owners have reported cracks developing at low five-digit mileage figures. There are many explanations, depending on who you ask, but no matter the cause, cracked pistons aren’t ideal for a diesel expected to perform as a workhorse hauler.

Other problems, unfortunately, carried over. For example, the 6.4-liter’s other Achilles heel is its emissions control system, mainly the EGR cooler. The 6.4L’s EGR cooler readily clogs up, to the point that mechanics were servicing trucks for EGR failure when they were basically still new. Thankfully, these were mostly resolved with the introduction of the 6.7-liter Power Stroke, which is widely considered a highly reliable engine and among the most reliable Power Stroke diesels ever made.

We selected these engines primarily based on unbiased perspectives, including data such as defective parts, common issues, service bulletins and issuances, and so on. These include primary sources such as Ford or the NHTSA, as well as technical specifications and in-depth breakdowns of the engines’ components.

Next, we considered the perspectives and rating systems of accredited periodicals such as Consumer Reports and Kelley Blue Book, as well as owner testimonials posted on those sites. We also took into account the opinions of professional mechanics and service technicians who worked on these engines. Finally, we also looked into owner reviews and testimonials from various sources to get a general picture of these engines’ reputations among end-users, common problems after years of ownership, and what sorts of fixes people have come up with (if any).

Because many of these engines are over 10 years old, we also evaluated reviews and owner reports from when these engines were new. This allowed us to establish a more complete picture of whether there was something actually wrong with the engines themselves or whether recent reports of issues are just the result of decades of wear and tear.