EGR Valve Test

 

Valve Opening Test

  • With engine at normal operating temperature and at idle, rapidly open and close throttle. Open throttle sufficiently to obtain at least 1500 RPM. Movement should be noticed in EGR diaphragm.
  • If diaphragm does not move, probable causes are: faulty vacuum signal to EGR, defective EGR diaphragm or defective backpressure sensor diaphragm (if equipped), or leaks in vacuum lines or connections.

Valve Closing Test

  • With engine at normal operating temperature and at idle, manually depress EGR valve diaphragm. RPM should immediately drop, indicating that EGR valve is not leaking and had been properly cutting off exhaust gas flow at idle.
  • If there is no change in RPM and engine is idling properly, exhaust gases are not reaching combustion chamber. Check for plugged passage between EGR valve and intake manifold.
  • If engine idles poorly and RPM is not greatly affected by manually moving diaphragm up, EGR valve is not closing off exhaust gas flow. Check for carbon between pintle, leaking EGR valve gasket or bad EGR valve.

Revised 1-31-2016

 

14 thoughts on “EGR Valve Test”

  1. My 87 xj won’t idle once hot. I recently put this jeep back on the rd after several years of pretty much sitting in the yard or occasional short trips. I have kind of went thru it. The injectors were all leaking so I replaced them . I put a radiator and water pump on. They were both bad. The fuel pump got very loud so I assumed it was bad and the no idle deal started. I pulled the tank and put a new one on and a new sock filter on the bottom( the old sock filter was full of rust) of a newer fuel pump I had with very few miles on it. I changed the fuel filter on the frame and disconnected the fuel line at the rail and blew thru with air just in case I had trash in lines. Figured this would take care of my problems. No. So I continue down ur list to clean the TB and idle air controller thinking this was the problem. Now when I crank up from cold it runs like a champ. However, once the motor is good and warm it idles like hammered crap and sometimes knocks off. When I crank it back up it usually is at a very high rpm, sometimes it slows down, sometimes not. I do have two parts jeeps and robbed a different egr valve and and idle air controller off one of the other jeeps. I changed out each part one at the time in case it fixed it then I would know which part was bad. Still has same condition though. Trying my best not to throw parts at this thing but, I am running out of patience and used parts. Lol. I am open to any suggestions u have. I have done all of ur tips that I feel mechanically competent enough to do. Feel free to call me if that helps. Don’t know if or when u might get this but, thanks in advance.

      1. Thanks for your help man. I have done tips 1-4. , 9-11,. 18, 28, 29, 31. I am just now getting comfortable enough to run a volt meter/ multi meter and I learned to solder last week. This has been over a period of probably 3 months. I know it is some little silly something because when it’s first crunk and not good and hot u can put a dime on the front of the valve cover and it purrs like a kitten.

        1. Thanks for the update. Great job of increasing your skill levels.

          Now you need to do Tip 5. Tip 27 if you wanna put your soldering and shrink tubing skills on a workout.
          After that is tested and repaired as needed, you can make a good adjustment on your TPS.

  2. Man knock on wood I figured it out this eve! Jeep still wouldn’t idle. Got to the point of not even when cold. ( At first it was only when hot). Anyway, I still didn’t trust my used fuel pump so I put a new one this eve. Still not idling. Next on my list was swap in a fuel pressure regulator off of my parts jeep. Still not idling. Next was another tps off the parts jeep. Immediately it ran good! So I was like ok maybe I just needed to adjust the tps. Aka my part is not bad just out of adjustment. Sure enough,. Went through ur steps on adjusting tps and it is running like a singer! Somewhere through the dirty fuel and switching out injectors it needed some fine tuning. Bingo. Thanks man.

  3. With the EGR Solenoid connector unplugged (engine running) I have no vacuum at the output on the solenoid. What would cause this?

  4. Hi Cruiser54, thank you for all the work you do… You are amazing for taking the time to help others with these amazing yet temoetmentemp 4.0 engines. I have an interesting issue occuring and I think it is all related to the TPS or very possibly the EGR. My TPS is only showing 1.94 volts no matter what I do. I have tried multiple TPS and still have 1.94 volts. I have grounded that directly to the battery and any other ground on the Jeep and it is still 1.94 volts. Most people that I see have 5 volts or just under, any idea why mine would only be pushing 1.94 volts?

    The issue I have is that once it warms up and gets out of the closed-loop it begins to want to die when you ease into the gas pedal. It is most noticeable if you are going uphill from a stop or if you want to test you can hold the brake and very slightly touch the gas. I am uploading a video now so you can see this. It runs perfect when it’s cold.

    When I unplug the EGR valve when hot it runs perfectly. Almost like the TPS is telling the computer to send the signal to the EGR solenoid allowing gases in that shouldn’t be let in at such low RPM. Does that make sense? I feel like if I can get to the bottom of the voltage issue on the TPS everything else should be fine. I have gone through and refreshed the grounds as I explained in the video.

    Any assistance you can provide would be much appreciated! Thanks again.

      1. Sorry for the delay. I didn’t get notified that you replied. And yes, 1.94V is what I get upon testing the voltage at the TPS.

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