Hey guys,
I think my EGR system may be malfunctioning. I am not getting any SES light, but I am failing emissions miserably. My NOx is off the chart! I was hoping to learn as much as I could about the EGR system so I can better diagnosis my problem. Here are the checks that I have already made...

1)Checked to see if there was vacum @ the solenoid "YES"
2)Checked to see if there was vacum @ the EGR valve while engine was reving. "YES"
3)Pressed up on diaphram while engine was idling to hear drop in RPM "YES"


I read the article in the Tech section. It helped me some, but I would like to know more. Mabey someone knows another check that I can make? I am planning on hooking a vacum gauge up to it soon to see exactly how much vacum I am getting. The EGR valve I have is fairly new. I was getting a SES code 32 in July... I replaced the EGR valve and the code went away. But a month afterwards... I couldnt pass inspection.


Thanks in Advance,
Mark B

 

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On a TBI, the only reference the ECM has for the EGR operation is the MAP sensor. When the ECM commands the EGR open, it expects to see a slight MAP increase shortly thereafter. If there is no MAP increase, the ECM presumes the EGR did not open.

What replacement valve did you install?

 

Dont know... I got it from AutoZone.

 

Jersey,

This is one time that you can consider yourself fortunate the you have a TBI. The EGR valve is a lot more accessible. If the replacement was one of those universal types that has orifice washers to calibrate teh EGR flow, you need to ascertain that the correct orifice is installed and staked in properly. While teh valve is removed, you should also plan to completely clean out the EGR passages of all carbon and deposits.

 

On a TBI motor the EGR needs a slight amount of backpressure to open, if you have headers and a freeflowing cat back exhaust, the EGR will not function properly. I have slightly enlarged the vacuum port in the valve to assist the opening and it resulted in lowering the NOX from 1300 down to 200-300. But be careful .010-.020 is a lot.

 

THANK YOU!!!!!

Thats probably my problem!!! My NOx went up after I installed a high-flow cat. So that probably pushed me over the limit as far as back-pressure goes. I will do the same thing you did. My NOx is at about 1300-1400 right now. Mabey if I do this, my problems will be solved! I was just about to start a new topic too. As you read... I wasnt getting a SES light before... But I put a new EGR valve on the car yesterday... And now I am getting a SES light!!!! Hahaha