How to Test an EGR Valve: A Simple Procedure

Updated on January 26, 2019
Dan Ferrell profile image

Dan Ferrell writes about do-it-yourself car maintenance and repair. He has certifications in automation and control technology.


Why You Should Know How to Test an EGR Valve

Learning how to test an EGR valve will save you time, money and some headaches. After miles of service, the exhaust gas recirculation (EGR) system—especially the EGR valve—will lead to engine performance problems due to carbon buildup, components mechanical problems, or vacuum hose leaks.

Depending on the particular problem, you'll notice symptoms like rough idle, pinging or knocking engine sounds, an increase in emissions, poor fuel economy, hard starting and even stalling. Without some troubleshooting, though, these same symptoms will mislead you into replacing an otherwise good EGR valve, solenoid, or miss a simple solution to your problem.

Here, we take a look at a simple procedure to troubleshoot a potential bad EGR valve, and a few tips to do some system cleaning, if necessary. In either case, I'd recommend you buy the vehicle repair manual for your particular make and model, if you don't have one yet. The manual will help as a reference, either now or later, to identify the exact type and components you have in your EGR system; help you in identifying passageways for cleaning the system, including the valve itself; and the correct steps if you need to replace the EGR valve. Not to mention all the help you'll get in future maintenance and repairs for your vehicle.

You can get fairly inexpensive aftermarket repair manuals from most auto parts stores or online. Or, if you don't want to buy the manual now, look up a copy of the manual in the reference section of your local public library.

And one more thing. Here, we'll deal with vacuum controlled EGR valves found in old model vehicles and some newer models using hybrid (vacuum-electronic) controls. New vehicle models come with electronically controlled valves, though (about six different types of EGR-valve control configurations exist today, and some late model cars have rid of the EGR valve entirely). Still, you can follow this guide along with the procedure described in your vehicle manual to test your EGR valve, if necessary.

To apply one of the tests to the EGR valve, you'll need a vacuum pump, which you can borrow-rent from a local auto parts store, if you don't have one. Other than that, you'll only need to use some common tools if you need to clean carbon buildup from EGR system passages.

Before testing, though, let's take a look at the purpose of the EGR system and what the EGR valve does, to make better sense of the EGR valve testing procedure.

EGR valve with carbon buildup.
EGR valve with carbon buildup. | Source

What Does the EGR System Do?

The EGR system in your vehicle uses the EGR valve to introduce measured amounts of exhaust gases back into the combustion chambers. These gases lower combustion temperatures. And lower combustion temperatures mean lower emission of harmful NOx (oxides of nitrogen) gases.

However, exhaust gases shouldn't flow continuously into the cylinders. Once the engine has reached operating temperature, gases begin to flow gradually as engine speed increases. When this flow pattern fails, you begin to notice a decline in engine performance. For instance, this will happen if the EGR valve fails to close completely as the engine idles, or fails to open when engine speed increases.

Unfortunately, problems in the EGR system and valve will happen sooner or later. Overtime, small carbon particles contained in the exhaust gases begin to stick and accumulate along EGR and intake system passages, clogging tubes, exhaust gasses channels and the EGR valve itself. Eventually, this will affect the valve's plunger mechanism as well, causing it to stick open or close. On top of that, EGR parts and components wear out and stop functioning properly.

That's when troubleshooting becomes necessary. You need to confirm whether the EGR valve has failed or carbon deposits have began upsetting EGR system and engine operation.

How to Test an EGR Valve

Locate the EGR valve

Look for a round, thick, metal disc about three inches in diameter. In most cases, you'll find it around the top area and to one side of the engine. You may need to look between and under some components on your vehicle. Also, you should see a thin, vacuum line connected to the top of the valve.

Still, depending on your vehicle model, the valve itself may have a different configuration. If you have trouble locating the valve, consult your vehicle service manual. Or visit an auto parts retailer on the Web, and enter your vehicle information to look for the EGR valve. Many auto parts stores online keep a database of auto parts photos or images for many vehicle makes and models. You may find a picture of the EGR valve for your particular model. That way you'll know what to look for.

Testing the Valve Stem Manually

The valve's metal disc houses a diaphragm, spring, and plunger to maintain the valve in the normally closed position. During operation, increase in vacuum pulls on the diaphragm, overcoming spring pressure to open the valve.

If you have good access to the valve, you may see small openings on the underside of the metal disc.

  1. Try to push on the diaphragm by sticking a finger through one of the openings of the EGR valve, if you have access to it — if you can't reach the diaphragm don't worry, you still can test the valve in the following sections.
  2. If the diaphragm doesn't move at all using finger pressure, you need to inspect EGR valve passages for carbon deposits restricting plunger movement (check the section EGR Valve and System Passages Cleaning below), or the mechanism has failed.

Testing EGR Valve Diaphragm Condition

Valve diaphragms suffer wear and tear as well. Eventually, they may start leaking exhaust gases. However, hidden from view inside the valve case, you need to do a specific and simple test to know the condition of the diaphragm.

  1. Apply the parking brake, block the wheels, and start the engine.
  2. Using a can of carburetor cleaner with the thin straw inserted into the tip, carefully spray a small burst of cleaner through the underside openings and towards the diaphragm.
  3. If the engine's rpm increases as you spray carburetor cleaner into the valve, the diaphragm is leaking and you need to replace the valve.

Testing for Stem Movement

  1. Start the engine and let it idle for about 15 minutes to bring it up to operating temperature.
  2. With the engine at idle, increase engine speed to about 2,500 rpm by quickly pushing and letting go of the accelerator linkage by hand, or ask an assistant to do it for you by quickly pressing and releasing the accelerator pedal.
  3. As you do this, watch the valve diaphragm movement. Use a small hand mirror for this, if necessary.
  4. If the stem or diaphragm doesn't move, disconnect the thin vacuum hose from the top of the valve.
  5. Place your finger on the opening of the vacuum hose you just disconnected.
  6. Increase engine rpm again as you did in the previous step. You should feel vacuum or a slight pressure on your finger tip, depending on the particular system type.
  7. If you don't feel a change in vacuum or pressure, likely the problem lies with the circuit that provides vacuum or pressure to the valve.
  8. Reconnect the vacuum hose to the valve.

Testing Valve Operation With a Vacuum Pump

  • With the engine idling at operating temperature, disconnect the vacuum hose from the valve and plug it with a thin Phillips-head screwdriver or a similar object.
  • Connect a hand vacuum pump to the EGR valve in place of the vacuum hose and apply 15 in-Hg of vacuum to the valve (if you don't have access to a vacuum pump you may borrow-rent one from a local auto parts store).
  • As you apply vacuum to the valve, check for diaphragm movement. Also, pay attention to engine idle. Idle should become rough or the engine should stall as you apply vacuum.
  • If the plunger doesn't move or the valve doesn't hold the vacuum you apply, replace the valve.
  • If you notice no change at all in engine idle operation, but the plunger moves and the diaphragm holds vacuum, carbon buildup is blocking passages in the EGR system or the valve itself. Continue with the following section to remove the valve and clean the passages.

Common Vacuum Type EGR System Checks

  • EGR valve plunger movement
  • EGR valve diaphragm leaks
  • Vacuum check
  • Vacuum hose condition
  • EGR system passage obstruction

How to Clean an EGR Valve

EGR Valve and System Passages Cleaning

If you suspect carbon deposits are blocking the EGR valve or system passages, remove the valve. You can also remove carbon deposits from some electronic EGR valves.

Tools You'll Need:

  • Set of sockets
  • Ratchet
  • Ratchet extension
  • Adjustable or crescent wrench, if necessary
  • EGR valve or carburetor cleaner
  • Dull scraper
  • Wire brush

Removing the Valve:

  • On some models, you only need to remove two mounting bolts. On other engines, you may need—in addition to removing the two mounting bolts—to disconnect the valve from a steel pipe that connects the valve to the exhaust manifold.
  • Depending on your particular car model, you may also need to remove one or more components to gain access to the valve.

Cleaning the Valve:

  1. After removing the valve, use an EGR valve cleaner, if possible. However, you can use carburetor cleaner or solvent as well. But don't let the harsh cleaner to reach electronic components attached to the valve or you'll destroy it.
  2. Apply the cleaner to the passages at the bottom of the valve, intake and exhaust passages.
  3. Use a dull scraper and wire brush to remove carbon deposits from the bottom of the valve, plunger and valve seat.
  4. If necessary, replace the valve gasket. If you can't find the valve gasket at your local auto parts store, buy paper gasket and make one yourself.
  5. Once you've cleaned the valve and passages, reinstall the valve.


Once you know how to test an EGR valve, apply the same steps every one or two years to service the system. Many car manufacturers suggest a specific interval to inspect the EGR valve and system. This simple task will help you keep emissions low, maintain good engine performance, and save on fuel.

Test Your Knowledge of the Automotive EGR System

view quiz statistics

This article is accurate and true to the best of the author’s knowledge. Content is for informational or entertainment purposes only and does not substitute for personal counsel or professional advice in business, financial, legal, or technical matters.

Questions & Answers

  • I have a 2005 dodge magnum 3.5L V6. It was running pretty good, but a bit bogged down and coded for the EGR valve, so we replaced it, and on the first startup and since it's roughly idling low at around 500 rpm and sputtering. It sounds like air may be escaping, but I don't know. Coded running lean on banks 1 and 2. p0404 and p0406. The paperwork says to replace the fuel pump, but nothing is wrong with my fuel pump. Please help?

    There seems to be a problem in the EGR circuit (P0404), maybe the sensor. Make sure vacuum hoses are well connected and in good condition. Also, did you check for build up around the ports? On some models, you need to dig deep into the intake to clear the passages.

  • I replaced my EGR valve and top vacuum hose, but the light of my vehicle is back on with the same code. What do I look for now?

    Double check the system and make sure there was no buildup in the valve/intake passages. On some models, you may need to remove the intake and clean buildup at the ports as well.

  • I have a 13 plate diesel Zafira, and the engine spanner light came on back last summer, lost power, then it was ok until six weeks ago. P0409 is the fault code. I did 17 miles before it broke down in Longleat! Could it just be the Air flow filter?

    The code points to an EGR sensor, check the sensor and the valve, it may be stuck. Other possibilities EGR solenoid and vacuum lines.

  • I have a 2004 ford explorer. The Check Engine light was on, and it was giving the EGR code, but running fine. I replaced the EGR valve & cleared the code. The car ran great for 47miles. But this morning it started idling rough and smoking with a strong smell of gas. Then, the Check Engine light started blinking. The new codes are P0300, 0301, 0302, 0303, 0316, P0172. Any suggestions? Could the new EGR valve be bad?

    The problem could be with the ignition system, or a solenoid related to the EGR valve is not operating correctly, making the valve get stuck and cause misfires.


    0 of 8192 characters used
    Post Comment
    • Dan Ferrell profile imageAUTHOR

      Dan Ferrell 

      6 days ago

      There could be a problem with the transmission. Make sure there’s enough fluid. If it’s got the right level, check the fluid for contamination or burnt odor. If it doesn’t smell right or has a dark, muddy color, the problem could be inside the transmission.

    • profile image

      alfred ferrarini 

      6 days ago

      I have a 2001 solara camry it runs great no rough idle or hard starting but no power and will rev high and not shift unless i back off on gas

    • Dan Ferrell profile imageAUTHOR

      Dan Ferrell 

      7 months ago

      Hi Davis,

      Check for air leaks around the MAF sensor and check the O2 sensor. Sometimes swapping O2 sensors can give you a clue. If the fault code follows the sensor, most likely it's bad. Other possible suspects are carbon build up around the throttle body bore and under the IAC, even a bad IAC.

      Hope this help.

    • profile image


      7 months ago

      I have a 98 ford ranger, threw an p0401 Egr code. I ran a vacuum to the valve, engine chugged down i replaced the ignition coil, the spark pugs, and wires, and the Egr tubing but with used tubing from a 2000 ford ranger. My truck, would surge driving, and all the instruments would fly around. When i replaced the dpfe or whatever censor it ran better but has started siezing and surging while i drive again, but after i deleted the egr code the only code that came up was o2 bank one before the cat... not sure what to do

    • Dan Ferrell profile imageAUTHOR

      Dan Ferrell 

      7 months ago

      Hi Phil,

      A common issue with an EGR valve is carbon buildup around the passages. Even if the valve is working fine, exhaust gasses will not get to the cylinders as they should. Check also the wiring for the solenoid and vacuum hoses connections.

      Hope this helps

    • profile image


      7 months ago

      Hi i have a asrta 1.9cdti. Code p0400.

      Ive checked egr and its working. Car is rough on idle.

    • Dan Ferrell profile imageAUTHOR

      Dan Ferrell 

      11 months ago

      Hi Ray,

      Just wondering, is it a flex fuel vehicle?

      Have you check the flex fuel module, I believe is under the dash.

      Good luck

    • profile image


      11 months ago

      we got a 2004 ford Taurus - the car will not start , crank, and fuel pump will not pump gas to engine - the on board computer states, " fuel comp err " have installed new fuel pump, fuel filter, ignition switch, neutral safety switch, crank and cam case safety switch, "(spark plugs and wires, per DLC test)" fuel pump modular. Tested all fuse and relays, tested incoming and outgoing voltage to fuel pump receiving 12v. all ground wires cleaned or replaced, can anyone give advice on the matter? Car quit at residents - and can not get car to a garage.

    • Dan Ferrell profile imageAUTHOR

      Dan Ferrell 

      11 months ago

      Hi Edrick

      Have you checked the fuel cut solenoid in the injection pump assembly - consult your repair manual, but I believe the resistance between the connectors is about 1-2 ohms.

      Good luck

    • profile image


      11 months ago

      I have got a Toyota condor 2litre ,1kz starts but doesn't rave up

    • Dan Ferrell profile imageAUTHOR

      Dan Ferrell 

      15 months ago

      Hi James,

      Check the intake ports where the valve sits, that's the most common fault in the system. And then check the system with the help of your vehicle repair manual to discard any faulty components or circuit fault.

      Good luck

    • profile image


      15 months ago

      Hello have 2008 f50 got a code to change egg pressure sensor valve I changed it cleared code ...... same code came back on check engine light

    • Dan Ferrell profile imageAUTHOR

      Dan Ferrell 

      21 months ago

      Hi Jason

      Have you scan the computer? It seems it's running rich. Possibly a sensor malfunction.

    • profile image


      21 months ago

      My car is stalling when it reaches its temp then it stalls and I smell gas out of my exhaust and my check engine light comes on seconds before it stalls

    • Dan Ferrell profile imageAUTHOR

      Dan Ferrell 

      23 months ago

      Hi Jagdish,

      Not familiar with that model, but it seems you got a problem with the head gasket, leaking oil into coolant. Take the car for a compression test.

      Good luck

    • profile image


      2 years ago

      Was very helpful, Was going to go and buy new one. But after testing. found

      that mine was OK


    This website uses cookies

    As a user in the EEA, your approval is needed on a few things. To provide a better website experience, uses cookies (and other similar technologies) and may collect, process, and share personal data. Please choose which areas of our service you consent to our doing so.

    For more information on managing or withdrawing consents and how we handle data, visit our Privacy Policy at:

    Show Details
    HubPages Device IDThis is used to identify particular browsers or devices when the access the service, and is used for security reasons.
    LoginThis is necessary to sign in to the HubPages Service.
    Google RecaptchaThis is used to prevent bots and spam. (Privacy Policy)
    AkismetThis is used to detect comment spam. (Privacy Policy)
    HubPages Google AnalyticsThis is used to provide data on traffic to our website, all personally identifyable data is anonymized. (Privacy Policy)
    HubPages Traffic PixelThis is used to collect data on traffic to articles and other pages on our site. Unless you are signed in to a HubPages account, all personally identifiable information is anonymized.
    Amazon Web ServicesThis is a cloud services platform that we used to host our service. (Privacy Policy)
    CloudflareThis is a cloud CDN service that we use to efficiently deliver files required for our service to operate such as javascript, cascading style sheets, images, and videos. (Privacy Policy)
    Google Hosted LibrariesJavascript software libraries such as jQuery are loaded at endpoints on the or domains, for performance and efficiency reasons. (Privacy Policy)
    Google Custom SearchThis is feature allows you to search the site. (Privacy Policy)
    Google MapsSome articles have Google Maps embedded in them. (Privacy Policy)
    Google ChartsThis is used to display charts and graphs on articles and the author center. (Privacy Policy)
    Google AdSense Host APIThis service allows you to sign up for or associate a Google AdSense account with HubPages, so that you can earn money from ads on your articles. No data is shared unless you engage with this feature. (Privacy Policy)
    Google YouTubeSome articles have YouTube videos embedded in them. (Privacy Policy)
    VimeoSome articles have Vimeo videos embedded in them. (Privacy Policy)
    PaypalThis is used for a registered author who enrolls in the HubPages Earnings program and requests to be paid via PayPal. No data is shared with Paypal unless you engage with this feature. (Privacy Policy)
    Facebook LoginYou can use this to streamline signing up for, or signing in to your Hubpages account. No data is shared with Facebook unless you engage with this feature. (Privacy Policy)
    MavenThis supports the Maven widget and search functionality. (Privacy Policy)
    Google AdSenseThis is an ad network. (Privacy Policy)
    Google DoubleClickGoogle provides ad serving technology and runs an ad network. (Privacy Policy)
    Index ExchangeThis is an ad network. (Privacy Policy)
    SovrnThis is an ad network. (Privacy Policy)
    Facebook AdsThis is an ad network. (Privacy Policy)
    Amazon Unified Ad MarketplaceThis is an ad network. (Privacy Policy)
    AppNexusThis is an ad network. (Privacy Policy)
    OpenxThis is an ad network. (Privacy Policy)
    Rubicon ProjectThis is an ad network. (Privacy Policy)
    TripleLiftThis is an ad network. (Privacy Policy)
    Say MediaWe partner with Say Media to deliver ad campaigns on our sites. (Privacy Policy)
    Remarketing PixelsWe may use remarketing pixels from advertising networks such as Google AdWords, Bing Ads, and Facebook in order to advertise the HubPages Service to people that have visited our sites.
    Conversion Tracking PixelsWe may use conversion tracking pixels from advertising networks such as Google AdWords, Bing Ads, and Facebook in order to identify when an advertisement has successfully resulted in the desired action, such as signing up for the HubPages Service or publishing an article on the HubPages Service.
    Author Google AnalyticsThis is used to provide traffic data and reports to the authors of articles on the HubPages Service. (Privacy Policy)
    ComscoreComScore is a media measurement and analytics company providing marketing data and analytics to enterprises, media and advertising agencies, and publishers. Non-consent will result in ComScore only processing obfuscated personal data. (Privacy Policy)
    Amazon Tracking PixelSome articles display amazon products as part of the Amazon Affiliate program, this pixel provides traffic statistics for those products (Privacy Policy)