1991 camry NOx (egr?)

[Hopkins530]

I tried to get the car inspected, 4 cylinder 100,600 miles, and it passed everything except for NOx, which was 4.71 ppm with a limit of 3.25. The car also rides a little weird when under 35mph, like there's too much feedback. Looking at the graph, the nox is highest when the car is under 35mph. I've been reading in to it, and I'm starting to think the egr valve is most likely stuck closed, but any suggestions would be greatly appreciated.

If anyone could guide me through checking or cleaning the egr valve or have any feedback, I'd be greatly appreciated. Thank you.

[Doctor J]

First of all, are the units correct (4 parts per million)?
The average NOx are 250 ppm, with limit of 730 max (in California) for ASM or I/M dyno test.
Two speed idle test is not using NO meter because the NO is near ) at idle speed and about 60 ppm at 2500rpm in neutral.
I need to know O2 content and HC reading.
The common places for EGR failure are:
EGR passage at intake plenum is plugged up
Egr vacuum modulator (Back pressure sensor) is burned up
plugged disconnected or leaking vacuum lines
over advanced timing
lean mixture
carbon deposits inside engine.

[Kep]

I found 4 pages of posts while searching “EGR valve”. Two that seemed appropriate were:
http://www.toyotanation.com/forum/t174729.html

http://www.toyotanation.com/forum/t171607.html

When I cleaned mine there were two nuts attached to studs from the throttle body and one compression nut underneath onto a tube from the exhaust. The nut underneath was a pain. I wound up using a crow’s foot type extension. Once I got it off the crud was real hard so I chipped of the big stuff first using a pick and small screw driver (don’t slip and damage the valve). Then I soaked it in a cleaner to get off the residue. When it is clean suck on the vacuum port and the valve should go up and down. Look down the tube (mine was clean enough) and the port to the throttle body (mine was plugged. Don’t leave any chunks in the throttle body). There is a vacuum hose at the bottom going to the vacuum modulator. Mine was plugged. I delicately used a small Philips screw driver to drill it clean.

While you’re in the neighborhood it would be a shame not to clean the IAC valve and the throttle body!

marc780 posted a good diagram and picture of the IAC at:
http://www.toyotanation.com/forum/t144688.html

Auto Zone has a WEB page on throttle body cleaning at: http://autozone.com/az/cds/en_us/090...rInfoPages.htm

Be patient,
Kep

[Hopkins530]

Thank you sirs, I just cleaned it out. Turns out the EGR valve was stuck closed, hopefully that did it. I'm going to take it to get inspected on monday. Thanks again.

[Doctor J]

Also verify that you have at least 10 inches of vacuum on the hose end that goes to the valve at about 2000 rpm.

[retiredat44]

Mine just failed Smog too. I suspect my EGR is bad, or plugged.. but I am having a shop do it.. cause I can get them to do it and have the state of California pay for it.



Every year mine Corolla get labled and a Gross Polluter. I just expect problems at every 2 year Smog inspection. 315,000 miles on the car. Always getting new parts it never ends...

[Doctor J]

Some budget cats are lasting less then one year.
If the engine has leaking exhaust valve o-rings, the monolitic (honeycomb) cats are destroyed very fast.