Can EGR system be bad with NO SES light?

[Mark B]

Hey guys,
I am still trying to pass inspection. I am thinking that my EGR system isnt working. My NOx readings are off the chart!! I have no SES light or code 32, but if my EGR system is bad... That would explain alot. I am going to test it tomorrow, but I was just wondering if its possible for the EGR system to be malfuctioning without throwing a code. (See sig for car info)

Thanks in Advance,
Mark B

[Benm109]

I'm sure it possible, I know a lot of 3rd gen guys that have bad 02 sensors but never get a code. Out of curiosity, do you get ever get code 32 at highway speeds? I would at least take off the EGR valve and clean it really good and test it, like you suggested. Don't forget to check for visible damage, too.

[Injuneer]

Have you had the cat checked? The 3rd Gens used the "split bed" cat, with a reducing catalyst in the front of the casing to break down NOx, and a seperate oxidation catalyst in the back of the casing, with the air pipe in between, supplying air from the AIR pump. If the front bed of the cat is bad, it could explain high NOx.

You will also get high NOx if the A/F ratio is on the lean side. That will elevate NOx, while reducing CO and unburned HC's. Running "hot" will elevate NOx formation as well.

All of these should be checked, along with the EGR system.

[EDIT] I just remembered.... this is the car with the cat replaced with a monolithic unit, and no intermediate air pipe connection? If so, I'd be a little suspect of the "universal" replacement.