Help Us Get to 1,000!




Trucks Submitted

Don't Miss Out on Our Gen-Y Hitch GIVEAWAY!

Complete 6.4L Powerstroke Emissions Guide

Guide to 6.4L Powerstroke Diesel Emissions Systems

If you’re a diesel nut like I am, you probably know that early emissions systems were the source of headaches and heartbreaks for many diesel owners. The 6.4l Powerstroke is no exception. Stricter emissions standards demanded something more environmentally friendly from auto manufacturers. Ford added a diesel particulate to their diesel trucks in 2008, and an extra EGR cooler to reduce their emissions footprint. Unfortunately, the emissions devices resulted in terrible fuel economy, tons of problems, and expensive repairs. Compared to GM’s LMM Duramax or the 6.7L Cummins of the same time period, the 6.4L Powerstroke appears extra susceptible to problems.

Types of Emissions Systems on the 6.4L Powerstroke

The three primary emissions systems tasked with lowering emissions output by the 6.4L Powerstroke are a diesel particulate filter, exhaust gas recirculation system, and a diesel oxidation catalyst. Here’s a description of what these three systems do.

Diesel Particulate Filter

The Diesel particulate filter helps in soot reduction. Have you ever seen black smoke emitted from an old diesel truck’s tailpipe? That smoke is unburnt hydrocarbons. The DPF, diesel particulate filter, captures these unburnt hydrocarbons. Every so often, the filter gets full and the truck goes through either active or passive regeneration. Exhaust gas temperatures get so hot that the remaining hydrocarbons burn off. While the process does help dramatically reduce soot emissions, it relies on diesel fuel to perform active regeneration.

During Active regeneration, diesel enters the exhaust stream. This occurs late in the exhaust stroke by a post-injection technique. From there, it exits into the manifold. The diesel effectively raise EGTs to a point where they can successful burn off any hydrocarbon residue from filter. Active regeneration causes a severe reduction in fuel economy and raises EGTs. If you idle or drive in heavy traffic frequently your truck is more likely to engage in active regeneration a lot.

Passive regeneration occurs naturally whenever you are driving. It occurs whenever EGTs or exhaust gas temperatures, reach a high enough level to successfully burn soot from the filter. It doesn’t cause lower fuel economy and is the ideal way to clean the filter. Passive regeneration occurs most frequently when you are driving on the highway or driving with a heavy load.

Exhaust Gas Recirculation

During the combustion process, harmful nitrogen oxides form. They are then released from the tailpipe, reducing our air quality. The EGR system dramatically lowers nitrogen oxide emissions. The exhaust gas recirculation system, or EGR, redirects harmful exhaust gases, cools them, and then re-introduces them into the engine. This reduces the amount of oxygen and the overall maximum combustion temperature, effectively lowering nitrogen oxide production during combustion.

The EGR valve is responsible for controlling exhaust gas flow. It is responsible for re-routing the gases. The EGR Cooler uses coolant to lower the temperature of the exhaust gases before they re-enter the engine. While the system does help reduce nitrogen oxide production, it also reduces the efficiency of the 6.4L Powerstroke engine. This is why race trucks delete their EGR systems, to improve overall performance.

Diesel Oxidation Catalyst

The diesel oxidation catalyst is the diesel version of a catalytic converter. In the DOC, hydrocarbons and carbon monoxide undergo an oxidation reaction. The oxidation reaction converts the hydrocarbons and carbon monoxide into water vapor and carbon dioxide.

Common 6.4L Powerstroke Emissions Problems

While emissions systems helped make the 6.4L Powerstroke more eco-friendly, they also experienced significant problems. Here are the most frequently encountered 6.4L Powerstroke Emissions problems.

Diesel Particulate Filter Clogging

With every diesel particulate filter, it’s not a matter of if the filter is going to get clogged, it’s a matter of when. Any filter’s primary responsible is the collection of something. The DPF collects soot which accumulates rapidly in a diesel truck exhaust. This is especially the case in early DPF systems. 9th injector designs that are used on trucks today are much more effective and they also don’t hurt fuel economy as much.

When your diesel particulate filter is clogged, it needs to be removed to be cleaned manually. Trucks with a clogged DPF typically go into limp mode. Speed is limited and overall performance is greatly reduced. This isn’t a cheap fix but it should be done immediately. While it is federally illegal, many people have opted to remove the DPF system and install a free-flowing straight exhaust. Performance can be tremendously improved, but it’s not recommended as you will fail any emissions inspections and it’s illegal. You can find out more about deleting emissions in this post.

The original DPF system on the 6.4L Powerstroke offers poor performance characteristics. Deleting it from your truck is illegal. What can you do? If your DPF system fails, invest in an aftermarket DPF. Bully dog makes an aftermarket Diesel particulate filter that greatly reduces the amount of regenerations and the amount of problems. They actually improve performance! Bully Dog claims their Performance DPF reduces EGTs by up to 12% and reduces back pressure by up to 44%! It can also be serviced very easily, thanks to a V-band flange. No cutting or welding required!

Oil Dilution

Oil dilution is common because of the fuel injection method for active regeneration. What is Oil dilution? Oil dilution is when diesel fuel contaminates your truck’s engine oil. It’s common to see a 6.4L Powerstroke gain a gallon or a couple of quarts of oil between oil changes. This is a major problem!

Diesel doesn’t offer the same lubricating properties as engine oil. Interior parts could wear much faster. Take note of how much oil you drain from your 6.4 Powerstroke. If you’re draining significantly more oil than you put in, the odds are you’re experiencing fuel dilution. Your 6.4L Powerstroke maintenance schedule should be consistent. Changing your oil every 3,000-5,000 miles can help reduce the effects of fuel dilution. Try checking your dipstick frequently too. Any signs of fuel dilution and excessive oil should lead to an immediate oil change!

EGR Cooler Clogging

If you’ve read my posts about the 6.0L Powerstroke, you’d remember that the EGR cooler was a problem for their previous generation diesel truck. Well, Ford gave their next truck, the 6.4L Powerstroke, two EGR Coolers. EGR Coolers are responsible for cooling hot exhaust gases before they re-enter the engine. Engine coolant cools these hot exhaust gases. Over time, engine coolant can break down causing an EGR to clog. A clogged EGR can cause you’re 6.4L to throw codes or even go into a limp mode. Luckily, the fix is relatively simple.

Consider investing in a coolant filtration device. Sinister Diesel and Mishimoto both make good 6.4L Powerstroke coolant filtration kits. You should also pretty regularly service engine coolant. The more frequently you service your cooling system, the less likely you are to experience coolant breakdown and clogging EGRs!

Want to Learn More About the 6.4L Powerstroke Diesel?

Check out some of our other 6.4L Powerstroke resources. Visit the page by clicking on one of the bulleted links below.

We Live & Breath Diesel.

Want to learn more about the latest insights in the diesel industry? Signup for our newsletter and stay up to date on the top trending topics!


Founder of Diesel Resource and a complete diesel head. Has a little bit of problem buying too many trucks. Learn more about him by checking out his truck.