Symptoms of a Bad EGR Valve

EGR valve passages plugged with carbon deposits.
EGR valve passages plugged with carbon deposits. | Source

The same symptoms that indicate a bad EGR valve can also indicate problems in other parts of the system. For instance, you can confuse engine performance problems stemming from a bad EGR valve with problems caused by failures in the spark plugs, the spark plug wires, the fuel filter, the fuel pump regulator, and various engine sensors. So, if you don’t do your troubleshooting, you may end up replacing parts unnecessarily and wasting time and money.

To recognize the potential signs of a failing EGR valve, it helps to know a little about an EGR valve: what it does, what it might look like, and how it works inside the combustion chambers or cylinders.

If you're already familiar with the EGR system, jump to the section below on “Symptoms of a Bad EGR Valve.”

Table of Contents

I. What the EGR Valve Does
II. Types of EGR Valves
III. How the EGR Processes Exhaust Gases
IV. Symptoms of a Bad EGR Valve
V. Troubleshooting


I. What the EGR Valve Does

The EGR valve is a small component designed to allow the flow of exhaust gases into the intake manifold in controlled amounts. As such, it's a simple valve that closes and opens as needed.

The EGR valve has one single job to do, regardless of the system configuration, type of control and number of sensors: that is, to either open and direct exhaust gases into the combustion chamber, or to close and keep them from entering.

Whenever you start the engine, the valve comes alive and waits in a closed position, blocking the flow of exhaust gases.

Once the engine reaches operating temperature and speed increases, the valve — either through vacuum or electronic control — gradually opens, allowing burned exhaust gases to enter and combine with the air-fuel mixture inside the combustion chamber. If you slow down sufficiently or come to a stop, the valve gradually closes and blocks the flow of exhaust gasses. And the process continues for as long as the engine is running.

After you shut off the engine, the EGR valve closes and remains in that position.

II. Types of EGR Valves

Gasoline and diesel-powered engines have various EGR system designs. Vehicles on the road today may use one of six different valve configurations.

On older vehicle models, you'll recognize the valve as a round, thick, metal disc about three inches in diameter, usually towards the top of the engine and on the side.

On these older models, a small-diameter vacuum hose operates a basic EGR valve. The hose connects the top of the valve to the throttle body or carburetor. The valve's metal disk houses a vacuum diaphragm, spring, and plunger.

Later models come equipped with electronic-vacuum EGR valves inside a small block or cylinder. The valve works the same way as in older models, except that an electronic EGR position sensor communicates with the car's computer for better control. You may see electric solenoids connected through vacuum lines to the valve as well.

Newer vehicle models use electronic EGR systems that may include additional components, even a digital valve that eliminates the need for vacuum control altogether.

A more radical design, implemented in a few models, was the replacement of the valve with EGR jets at the bottom of the intake manifold.

Some newer high-efficiency engines, for example those with variable valve timing (VVT), don't even use an EGR system.

Different Types of EGR Valves
Vacuum-controlled EGR valve
Back-pressure EGR valve
Electronic vacuum-controlled EGR valve
Digital EGR valve
EGR jet (in place of EGR valve)

III. Processing Exhaust Gases

The outside air picked up through the engine's intake manifold contains close to 80 percent nitrogen and 20 percent oxygen, along with small amounts of other elements. When outside air combines with the fuel and ignites in the combustion chamber, temperatures can reach above 2500o F (or 1370o C). Combustion at these temperatures burns the usually inert nitrogen gas, creating oxides of nitrogen (NOx) gases, which cause air pollution and human health problems.

However, when the burned exhaust gases are introducted back into the combustion chamber through the EGR valve, extreme temperatures decrease, inhibiting the formation of NOx gases.


IV. Symptoms of a Bad EGR Valve

An EGR valve can fail in two ways: It can be open all the time, or it can be closed all the time.

If the EGR Valve Sticks Open:

This will cause a continuous flow of exhaust gases into the intake manifold. You'll notice one or more of the following symptoms:

  • A rough idle upon starting the engine (that is, when the engine is cold) and sometimes at a stop light or while looking for a spot in a parking lot (that is, at low engine speeds in a warmed-up engine).
  • Stalling when the engine idles.
  • Increase in fuel consumption.
  • A slight — or strong — fuel odor while operating the vehicle, because of the increase in hydrocarbons leaving the tailpipe (see the next symptom).
  • Emissions test failure. When the engine is running at low RPM, lower temperatures in the combustion chambers prevent all the fuel from burning, so the flow of unburned hydrocarbon gases coming out of the tailpipe increases significantly.
  • The Check Engine light (or Malfunction Indicator Light, MIL, depending on your model) illuminates on your dashboard.

If the EGR Valve Sticks Closed:

This will permanently block the flow of exhaust gases into the intake manifold. You'll notice one or more of the following symptoms:

  • A pinging or tapping noise coming from the engine at low RPM (at speeds higher than idle). The noise is the sound of early ignition of the fuel when it meets high temperatures.
  • Loud detonations. A second ignition can happen after the normal ignition, and the two can combine with enough power to potentially cause serious engine damage.
  • Your car fails the emission test. High temperatures in the combustion chamber allow the excessive formation of oxides of nitrogen, which are released through the tailpipe.
  • The Check Engine light, or Malfunction Indicator Light (MIL), illuminates on your dashboard.

V. Troubleshooting

Are the symptoms above a sign of EGR problems?

Not necessarily.

An increase in hydrocarbon emissions isn’t necessarily caused by a stuck-open EGR valve. Problems in other systems may cause this same symptom as well: a leaking fuel injector, bad ignition timing, bad cylinder compression, bad oxygen sensor, or other problems.

Similarly, an increase in NOx may be caused by a vacuum leak, a clogged fuel injector, low fuel pressure, a leaking head gasket, or other problems.

A rough idle may be caused by a faulty ignition coil, a vacuum leak, or an ignition system problem.

Because these symptoms vary and be caused by different issues, don’t hesitate to troubleshoot the EGR valve and other system components to try to narrow down the problem. This article, How to Test an EGR Valve, gives a series of troubleshooting procedures on vacuum and electrical vacuum-controlled EGR valves, and will help you find out if the problem is your EGR or something else.

Also, because cars with electronic EGR valves will have a Check Engine or MIL light on the dashboard, in these cars you can find out what engine system malfunction triggered the light. With an aftermarket scan tool, you can pull the trouble codes from the computer's memory and see what system or components are causing the problem. Then, you can try to find the fault with the help of the vehicle repair manual for your particular car make and model.

Test Your Knowledge

Locating the EGR on a Corvette and on a Truck

More by this Author


Jeremiah 7 months ago

Thanks for the article. My only response is to the replacing unnecessary parts wasting time and money. My car has almost 150 thousand miles on it so it would just be replacing the part before it went out.

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Dan Ferrell 7 months ago Author

Hi Jeremiah,

Once miles accumulate, maintenance becomes a priority.

Thanks for stopping by.

Peaches 7 months ago

Thanks for the great info! I have every single one of the symptoms for the open valve, (Okay, well actually our MPG seems like it has INCREASED). As we had our injectors replaced about two years ago, we are really hoping that the new EGR valve will solve our problems! We are also at 150K on a Ford F250 Diesel. Keep your fingers crossed for us please!

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Dan Ferrell 7 months ago Author


glad the info helped. Good luck.

chris 6 months ago

hi Dan,

my mk4 golf 1.4 petrol has lost power max speed is 70mph now as the engine light is on been advised my egr is needing to be replaced car is 14 years old and has 128,000 on the clock, will there be damage to any other part of the engine??

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Dan Ferrell 6 months ago Author

Hi chris,

Hopefully not. If it's just recently that the light came on, remove and check the valve. See if there's much carbon build up. You might want to check your repair manual and see the particular check procedure for your model.

Good luck.

Louis 5 months ago

Hi Dan, In last couple of weeks my ford s max 2012 car battery went flat and i had a jump start more than 10times. When engine off, I noticed a 1.5minute beep and click sound from egr valve and it will stop for 30 sec and this will repeat around 30 min from engine stops. Also i can see the above egr valve open symptoms like odor of burned fuel. From saturday i got a malfunction symbol in the dash board and I have given the car to Taylor auto electricians and they said they did not find any drains and they replaced the battery and charged me £209 for diagnostics and battey replacement. I already mentioned egr sound to them, but they said this is quite normal. But still i can see the malfunction symbol in the dash board with computer message for malfunction and now the engine is running in limp mode. Yesterday I have disconnected the electrical connection to the egr valve and drove the car and i can see the engine yellow symbol in the dash board without any computer malfunction message and i got full engine power and limp mode removed, but the computer message comming back when reconnecting egr valve. I assumes that something happened in the electrical side of the egr valve. Could you please advise if i am wrong. Thanks..

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Dan Ferrell 5 months ago Author

Hi Louis,

You didn't mention if the shop checked any TSB (technical service bulletins) on that particular model. It seems to me there is a malfunction in the circuit.

Since you already spent some money for a diagnostic without any results, why don't you go over to this forum:

These guys are pro and it's worthwhile signing up. Give them all the info on your car, the symptoms, tell them what they did in the shop. They'll even check for any TSB for you.

Good luck.

cherish 4 months ago

Will a bad erg valve issue stop your car from starting but start after jumping

Pumpturbinator 3 months ago

Just bought My 04 MSM Mazdaspeed MIATA & it will not pass smog. The tester says EGR code reading incomplete. It doesn't give a code or store a code. Now I tried 3 or 4 times to drive the car in high gear then letting it slow down in high gear for over 20 seconds each time. I have driven the car 400 miles. The smog guy took it driving for a hour thinking he could get it to reset. I keep trying to reset the EGR but it doesn't work. Also pulled EGR and cleaned it. Then pulled intake to check it. This is a very clean car almost like new. 65000 miles. Very well taken care of by a old man in Thousand Oaks Ca. Everything is stock. The car runs good but has a rough idle. We have it set about 800-900 rpm. I also checked for a vacuum leek with a propane torch. All checked out good. New plugs, wires, oil change. Do you think Mazda can reprogram the ECU ? What do I try next before I spend big money at the dealer ? Or who do I ask ?

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Dan Ferrell 3 months ago Author

Hi Pump

It seems the ECU should be throwing a code, specially if the EGR has failed. If you're sure there's no problems with the vacuum hoses or EGR sensors' connectors and wires, take the car to a good shop and have diagnose the problem. Hopefully you'll be able to fix it on your own with the diagnostic at hand.

Good luck.

Denny 3 months ago


My girlfriend has a 2004 F250 with the 6.0. When she accselerates it makes a loud whining noise. We have replaced the turbo completely. We have replaced some other parts as well trying to trouble shoot it but still nothing. Could it be from the ERG or the AFRG? Wondering if you have any insite on what could be the issue.

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Dan Ferrell 3 months ago Author

Hi Danny

Wonder what made you think it was the turbo. It's hard to tell without other potential clues. Have you thought of the drive belt? If you rev it up at idle, does it make the same noise? If so, you can use a piece of hose to listen to the pulleys, and idle pulley. A slipping belt whines when worn out or a pulley is out of alignment. If that check fails, stop by this forum:

they get access to TBS just in case.

Don't change components until you get a more accurate diagnostic.

Good luck.

Terry 3 months ago

Hi there,I have a Toyota avensis 2.2 d4d car,my car will not start ,I had a crecorder in the car from the previous owner and I took it out ,it will not start now,I plugged the crecorder back into the car and still no luck,I have had a computer on it and it said egrvalve on computer,I have taken out the egr valve and cleaned it ,still nothing ,could it be ecu error and what do I do

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Dan Ferrell 3 months ago Author

Hi Terry,

Make sure to check any EGR sensors, electrical connectors and wires. The computer is pointing you in the direction of the circuit not necessarily to the valve, although this could be your problem. Use the repair manual for your particular model to test the EGR valve and solenoid to pinpoint the problem.

Good luck

Jim 2 months ago

Dan, I have a 93 F150 5.0 and so far have replaced throttle position sensor, EGR speed sensors and exhaust manifolds. Check engine light still comes on and after it comes on, I notice a decrease in power, especially on hills. Any suggestions?

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Dan Ferrell 2 months ago Author

Hi Jim,

First check what diagnostic trouble codes (DTCs) are stored in the computer. If you don't have a scanner go to an auto parts store, usually they'll retrieve the codes for your. When reading the codes, remember that the computer can only point you to the circuit it detected the "error" coming from; it won't tell you if an specific component went bad. You need to test the sensors, actuators, connectors, grounds, incoming power, etc on that particular circuit to find the fault.

If a code points to the EGR, test the egr, the egr-sensor, any vacuum connected to it, electrical connectors, wires, etc.

Good luck.

Dilly 2 months ago

I have a Mini Cooper s & when I'm in a traffic jam, stop start for about 20 mins the engine fan comes on, followed by the turbo light coming on then the engine coughing & spluttering & dying! Could this be the egr valve? It only happens when it gets hot & in this sort of traffic.

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Dan Ferrell 2 months ago Author

Hi Dilly,

Check for any DTCs from the computer first, you can go to autozone or your local auto parts store. Have them pulled any codes from the computer and start from there.

Good luck.

Berttrim 2 months ago


I wonder if someone could give me some information about a problem with my 1999 Nissan quest. This is virgin territory for me. A rhythmic bucking while standing at lights or in drive. Regular driving is better, but with the occasional bucking. When starting from cold it seems quite normal until warm 5 to 8 min. New alternator, not an ignition problem. Tested throttle body housing. I'm guessing EGR plugged, or Cat. No codes on dash. Before I dive headlong into this, does anyone have any other ideas. Thanks

eldrun 7 weeks ago


I have got a jeep cherokee 2004 2.8 diesel. I am blowing white smoke through the exhaust.performance is affected and also fuel consumption is very high. please advise on my option on fixing the problem.

it was initially thought that the turbo was was bad and burning out oil so had that replaced and was told after a few 100 mile it should stop but still have not. so question is is it my injectors or EGR valve or something else


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Dan Ferrell 7 weeks ago Author

Hi Berttrim,

It wouldn't hurt to take a look at the EGR passages. If you haven't done in the last couple of years, there might be some gunk stuck in there. The valve may open but buildup may prevent gases from flowing back in. Take a look and clean up as much as you can.

Good luck.

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Dan Ferrell 7 weeks ago Author

Hi eldrun,

have you done a compression check yet? If the white smoke is continuous you might have a blown gasket. You can do the compression check yourself with a special gauge, go to this link for the steps:

Good luck

slkdnichols 6 weeks ago

I have a 2008 Dodge Charger with the 3.5L. I just had the timing belt replaced (I know I am late) and had recalls done on the same day. The recalls included the driver side airbag, FOBIK and ignition. Since that day, I have been having issues with the car. It is idling a little rough, I have lost hp and it doesn't shift down properly. In addition to that, I have had issues starting the car. I will turn the key all the way, let go of the key and the car starts after a second or two. Yesterday, I turned the key, I waited for the delay, the car started and then died... and then started again by itself without me touching anything!!! The dealership says that it isn't an ignition issue and the mechanic says that they didn't do anything when changing the timing belt! oh, one last thing, I was on my way home last week; the traction control and ESP/BAS lights both came on. They went back off after I let the car sit for a while at the house (turned off). HELP

slkdnichols 6 weeks ago

In addition to the comment above... I thought it might be the EGR valve that is having the issues... and it is just a coincidence that it happened at the same time as the ignition and timing belt were replaced. :)

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Dan Ferrell 6 weeks ago Author

Hi slkdnichols,

it does sounds like an ignition issue. If they didn't replace anything from the ignition system maybe they left something unplug or not well connected (?). Did they tell you what the ignnition recall about? Did they replace something? Also, if they moved-replace something and system service is overdue, worn out ignition components will not handle power properly as per the new components.

I'll start with this recommendations.

Good luck

Annie 5 weeks ago

Hi Dan,

I hope you can help. I have an Audi A4 tdi 2008 Cabriolet.

Three weeks ago I stared getting some white smoke from my exhaust and an almost sweet smell with it. I took it to a garage where they had a good look. After a couple of weeks they have changed the EGR Cooler, rocker cover unit ( due to heavy sludge build up) 3 engine flushes, new engine oil filter, new air filter and replaced the engine oil.

I have driven it home from work for the first time since having it back (30 miles) and noticed smoke from under the bonnet. I opened the bonnet and there was smoke coming out from around the oil cap....

Is this normal after all of the work I have had done? I have just spent the best part of £900 on the repairs and I am now really worried about this new problem.

Thank you in advance.


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Dan Ferrell 4 weeks ago Author

Hi Annie,

sorry for the late response. You definitley need to have it check. That's not normal. Did they put too much oil in it? Did they put everything back the way they were supposed to? I hope that by now you've taken the car back and have it checked.

Good luck.

Mark Williams 4 weeks ago

It seems Dan that I have high detonations when I go up hills on roads when I'm pressing on the gas pedal. My vehicle is a 1999 Chevy S10 truck, LS extend cab 4 cylinder 2 door and I have no EGR sensors that will trigger the EGR valve for my light to come. I did change the Fuel Filter, the tensioner and pulley, 3 TCC solenoids in the transmission since 1 did come up for the service engine light, and cleaned off the Idle Air Control Valve and passage. With high detonation while driving up hills , do you think my EGR valve is bad now or I should check my EGR valve out too? Also, new Air Filter, Oil Filter has been replaced but same sound still, plus sometimes the truck jerks after 1st gear, it can't be any solenoids in my Automatic transmission because they're new.

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Dan Ferrell 4 weeks ago Author

Hi Mark,

It'll be a good idea to check the EGR valve as well and have you tried to scan the computer? Any codes? Check for possible misfires. It seems more than one symptom due to maintenance.

Good luck.

Arthur Leite 3 weeks ago

Hi Dan, I have an Mitsubishi Pajero/Montero Full Diesel V98W motor and almost thee weeks ago motor light turned on, I passed scan show us EGR fail, I oppened it an complete carbonized so I cleanned careffuly with Wd40 reset but motor light return and still ON, so my doubts are: 1- Is possible to drive car with this EGR Valve? Is it cause any damage? 2- Mitsubishi EGR is eletronic so how can I test it? 3- There are some sites that reccommend close/cover EGR open for definitely, is it possible and make sense?

One sympton I identified is, when turno of the car by key there is a delay for motor shut of about 1 or 2 seconds, only turn of, no more issues...

Thank you in advance.

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    Dan Ferrell14 Followers
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    Dan Ferrell writes about do-it-yourself car maintenance and repair. He has certifications in automation and control technology.

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