2 Signs That High Mileage Diesel Owners Need to Perform This Overlooked Maintenance Task – Jalopnik

Diesel vehicles are usually quite specialized. There was a time when fuel was really under pressure, and while many automakers tried it as a mainstream fuel, the industry – at least in the US – quickly decided that diesel was actually best reserved for large trucks. Although lacking in noise and performance, diesel engines are incredibly durable and offer great torque, making them perfect for towing and towing. As such, diesel-powered trucks are often used heavily, gaining increasing mileage as reliable workhorses.

Regular maintenance is necessary to keep your engine running as smoothly as it should. But there’s one job you won’t see on the truck’s maintenance plan: cleaning the intake manifold. As the miles add up, carbon and soot buildup will restrict manifold airflow, which can harm both your truck and its performance.

This restriction of airflow is mainly caused by the exhaust gas recirculation valve (EGR), a standard recommendation for emissions reduction on modern trucks. The EGR valve absorbs some of the exhaust gases and directs them back into the combustion chamber via the intake manifold. This reduces harmful emissions and can even improve fuel economy, but it also creates a thick layer of carbon in the intake. You don’t have to pry your intake manifold loose every time you service it to see how it behaves. Instead, try to look for reduced performance or fuel economy, which are signs the car needs to be cleaned.

The intake manifold directs air to your engine. If the intake manifold is damaged due to a thick layer of carbon on the inner walls, less air can enter. This has a direct effect on the way your truck moves on the road. You may start to feel sluggish, have to work harder to maintain a steady speed on highways, and notice that the truck feels a lot more tense when you try to accelerate.

Of course, there are a lot of reasons why your truck might not be performing as well as it used to. But if no engine codes are showing and you’re having trouble diagnosing the problem, this could be the answer. A clogged manifold is also often accompanied by a lumpy idle as the engine struggles to draw in the proper and desired amount of fresh air, so that could be a sign that your intake manifold may need cleaning.

Fortunately, cleaning the manifold is usually not a difficult job, although it can sometimes be time-consuming. If a new intake manifold is cheap enough, consider simply installing a new one instead of refurbishing your old one. It is suggested that the intake manifolds need to be cleaned an estimated every 50,000 to 45,000 miles, so this is not something you need to worry about every oil service or inspection.

Many diesel truck owners log huge amounts of highway miles each year, so it’s likely that a drop in fuel economy will be noticed. While a clogged intake manifold won’t directly change your car’s fuel economy, if performance decreases and acceleration is sluggish, you will likely have to work the engine harder to maintain comfortable speeds.

If you notice that fill-ups are becoming more frequent and your monthly diesel bills are increasing (which is especially noticeable since diesel is more expensive than gasoline), stop and think about the last time your intake manifold was cleaned. There are numerous ways you can clean the manifold, some of which require removing the unit. Not every method requires this, but if you want to make sure the job was done thoroughly, removing it will allow you to physically see when all the carbon and dirt has been removed.

If the cleaning has been successful, you should know this immediately during your next ride. Your idle speed has been restored, the truck’s performance is back to where it should be and you will hopefully notice an improvement in fuel economy. However, you may have to wait until the muscle memory wears off so you no longer have to just move it.