Skip to content

EGR Valve Cleaning How-To: Carbon Deposits Be Gone!

Cleaning this EGR valve reduces NOx emissions and extends the life of your engine.

The exhaust gas recirculation (EGR) valve plays a vital role in keeping pollutants out of the environment and maintaining the overall health of your car’s engine. It works to prevent the formation of nitrogen oxide (NOx) gases, and it works pretty hard. Over time, the valve itself can accumulate carbon deposits from repeated exposure to heat and other detonation byproducts, causing system blockages or the valve to get stuck open or closed. Knowing how to perform an EGR valve cleaning is a helpful trick to add to your repertoire, and a quick fix if your engine is suffering any of the associated negative symptoms.

ObNOxious Buildup

The EGR valve allows exhaust gases to flow back into the combustion chamber at the appropriate times and levels. This helps keep combustion temperatures lower, inhibiting the formation of NOx gases. NOx gases are bad for the environment and human health, and the deposits and high heat that create them can also seriously damage your engine. Left unchecked, a clogged EGR valve can cause engine knocking (untimed detonation), and this will eventually destroy the inner components of your engine, requiring overhaul or replacement. Imagine all that hassle over a small component that you can easily clean or replace.

Time for a Change

The signs of a clogged EGR valve can be misdiagnosed as coming from other underlying issues, so it’s good to rule those out with the help of a professional or direct inspection. Basically, you might notice poor performance, rough idle and poor acceleration if the valve is stuck open, and the smell of gas, engine knock and poor fuel economy if the valve is stuck closed. For OBD-II equipped vehicles the check engine light may come on with the code P0401 stored. The valve should be cleaned or replaced every 50,000 miles or so, and it’s a good candidate to add to your annual checkup list.

A Clean Start

An EGR valve in poor condition.

The valve is usually located on the top of the engine near the throttle body or air intake. Start the EGR valve cleaning by examining the outside and connected components for damage. Is the connected hose cracked and brittle? Are the electronic connections (if there are any) sound and clean? The valve itself is smallish and usually held into place by two to four bolts. Remove these and carefully separate it from the gasket. If the gasket breaks or is otherwise in bad condition, you’ll need to replace it. You’ll see carbon deposits easily if they’re there, and they’ll be black, hard and cruddy. Always make sure nothing – deposits, pieces of gasket, etc. – falls into the engine. It doesn’t hurt to grab a utility vacuum and suck up any crud that comes loose. Do NOT use compressed air, as it can blow crud into the engine as well as back into your face an eyes.

Next, spray carburetor cleaner onto the deposits, and be careful to immediately wipe off any spray that gets on plastic or electronics. Use a wire brush or pipe cleaner to scrape out the deposits, but make sure not to damage or gouge mating surfaces. Repeat the spraying and scraping until it’s clean, wipe it clear of any small particles, then replace everything, and finally tighten the bolts.

Cleaning the EGR valve is a simple bit of maintenance that pays off big time in extending the life of your engine. It’s also necessary to pass your annual vehicle inspection, so it’s critical to keep it in good condition. Just make sure that you clean it properly to avoid unintended damage if you’re not replacing it outright.

Check out all the fuel & emission system parts available on NAPA Online or trust one of our 17,000 NAPA AutoCare locations for routine maintenance and repairs. For more information on EGR valve cleaning, chat with a knowledgeable expert at your local NAPA AUTO PARTS store.

Photos courtesy of Blair Lampe.


Blair Lampe View All

Blair Lampe is a New York-based professional mechanic, blogger, theater technician, and speechwriter.  In her downtime she enjoys backpacking wherever her boots will carry her, rock climbing, experimental theatre, a crisp rosé , and showering love on her 2001 Sierra truck.

Leave a Reply

Your email address will not be published. Required fields are marked *