The Ford F-150 may be America’s best-selling truck, but it’s not without its problems. As the most-recalled vehicle sold here, some problems are due to bad design. But considering how pickup trucks are used, some issues crop up for the same reason people get bad knees: age. There are several Ford F-150 problems that only pop up after the truck’s been on the road for 100,000 miles. Here are some of the most common.

Rough-running engine

Raybuck Auto Body Parts warns that 12^th-gen F-150s (2009-2014) often start to run and idle roughly. This was particularly problematic for the 2010 model year, which is on our list of F-150 model years to avoid. The rough idle wasn’t due to the turbocharged EcoBoost engine—that didn’t come until 2011.

What happened was the exhaust gas recirculation sensors were getting sticky. Carbon from the engine was accumulating on the sensors and clogging them. Although diesel engines are usually the ones that make more soot, it can happen in gasoline trucks, too. A clogged mass airflow sensor in particular causes a rough idle.

Ford experts stated that drivers change the MAF and EGR sensors every 100,000 miles. At that point, the sensors have begun wearing down, which can cause further engine imbalance and rough idle. While the more-affordable EGR sensors should be replaced, the MAF sensor can be cleaned with an MAF-specific cleaning solution.

Spark plugs breaking off

Although some types of spark plugs should be replaced every 20-30,000 miles, modern plugs can often last up to 100,000 miles. The plugs in 2004-2008 Ford F-150s were actually designed to not need a service until then. Unfortunately, as both Raybuck and Ford Problems describe, that 100k service interval came with an asterisk. And a major headache.

First of all, that’s outside the truck’s basic warranty. And second of all, waiting until 100,000 miles to change the plugs meant dealing with a very annoying problem. Over time, soot starts to accumulate on spark plugs. That’s what caused my first car to shut down on the way to work. Luckily, there are cleaning solutions designed to remove these soot deposits. It’s a shame no one at Ford told that to owners or mechanics.

For the 3-valve engines used in the 2004-2008 F-150s, Ford created a unique 2-piece plug. And the Blue Oval specified a 100,000-mile service interval. But, if the plugs weren’t cleaned by 30k, the carbon deposits would cake around the electrode so much, the plugs got stuck. Then, because of the 2-piece design, when the mechanic tried to remove the plugs, they broke in half. Making removing the plugs even more difficult—and expensive.

Head gasket leak

Another problem area noted by us and Raybuck is the 2009-2014 F-150’s passenger-side head gasket. Sandwiched between the engine block and cylinder head, the head gasket is what keeps the explosions inside the combustion chamber. It also, according to Mobil, keeps coolant and oil from mixing together. It’s this task that 12^th-gen F-150 head gaskets struggled with.

After driving 160,000 miles or so, F-150 owners would start to smell burnt oil. Oil had begun leaking into the engine and onto the starter from the passenger side. According to the Ford Truck Enthusiasts site, this was due to overheating, oil overfilling, and the gasket’s sealant disintegrating. Raybuck also adds that many ’09-’14 F-150 head gaskets were improperly installed, adding to the problem.

Repairing the issue requires removing quite a bit of engine, and is best left to a certified mechanic. But completely replacing the head gasket isn’t necessary—using a stronger epoxy as a sealant is usually enough. It’s also cheaper.

Other Ford F-150 problems

Although the stuck spark plugs are a problem that shows up after 100,000 miles, there is another spark plug issue that can pop up much sooner. As we’ve noted before, the Triton engines in 2004, and even ’97-’03 F-150s can sometimes randomly spit out their spark plugs. Although it wasn’t a Ford, this is also what killed my first car. The exact reason isn’t known, although Ford Problems state the most common theories involve the aluminum cylinder heads.

The metal and thread design, allegedly, are too weak to handle the forces involved. In addition, the spark plugs were supposedly under-tightened and over-torqued, letting them vibrate in place and wearing the aluminum threads away. Considering my first car had aluminum cylinder heads, there may be some truth to this.

But not all Ford F-150 problems come from production flaws. A user posting on the F-150 owner forums asked what issues could crop up after 100,000 miles. After bringing up the spark plug issues, another forum member suggested the rear axle bearings would probably need to be changed. Not because they were flawed, but because of normal wear-and-tear.