EGR valve vacuum reading

[AbusedJalopy]

We finally got around to fixing all the vacuum leaks on our car and thoroughly cleaed the EGR valve out since we failed the NOx part of the emissions test, and the EGR has a big role in that. The problem I now have is that I don't know what the vacuum gauge is suppose to be reading when testing the EGR. The manual says to plug a Tee fitting to the EGR so you can get a reading on the vacuum gauge to with the EGR still working, so you get an accurate reading. It then says to check that at idle there is no vacuum, and at 3000rpms there is low vacuum. My question is, what is there idea of low? Ours shows just under 5 (in of Hg) when its at 3000rpms, but is this doesn't seem like enough to open the valve fully. The only thing I can think of is that either our EGR vacuum modulator (the round thing that sits next to it) is faulty or it mentions that engine load affects the EGR, so maybe its not reading high because we're just free reving the engine. Anyone have ideas of what it's actually suppose to be or can anyone test theres? I want to make sure it works since we only get one free smog re-test. Thanks in advance.

[takza]

There is a writeup on the EGR in the Repair section....some info on ways to pass emissions.

NOX might be affected by ign timing? ...might search newsgroups or yahoo?

There are some threads on this site on passing emissions.

" * For the EGR vac line test with engine warm and at 3000 RPM I got a reading of 3" Hg. Saw that the EGR valve opens fully at around 4" to 5" Hg. "

That is what I found....'83 California emissions


After I replaced the O2 sensor, the EGR made the car undrivable....so it's OFF now. Think that the vac modulator isn't up to par...didn't exactly test out that well.

Now have a used vac modulator that I'll try this summer.

[2wagons]

When I was trying to get the 87 up to speed, I too checked the EGR. Cleaned the valve etc. Put the thing back on and it ran horribly. Inspected the vacuum lines and found that both the tubing and the steel lines were clogged! Also foudn that the some of the oher lines were clogged. A little carb cleaner, the lines cleaned out, and the EGR performed much better. Also check the modulator and make sure it is clean and works to spec. Just my 2 cents...

[AbusedJalopy]

I found the post on the EGR valve, but not on passing emissions. I'm pretty sure it works from what everything I've read tells me so far. The car runs like crap compared to how it ran before we got it working. I'll be disabling it as soon as we pass, if we do. Our numbers were 3000 for NOx when max allowed was 1300, so I don't know if this one thing will reduce it by that much.

Also, I read up on the ignition timing and it appears that retarding it will greatly help reduce NOx. One problem is that they check our timing here to make sure you're not "cheating" to lower the NOx this way. Ours actually was set to 8° when being smogged and it's suppose to be 5°, so they must not be too strict. So next time we'll try lowering to maybe 0-2°. Should I temporarily block the vacuum advancer on the distributor to keep it from upping the timing like it's suppose to? Thanks for your input so far, please offer any other suggestions.

[Adelard of Bath]

Just to throw this into consideration, when I was messing around with mine, I put my vacuum pump on the EGR itself and found that the diaphragm in there was ruptured or something, as it wouldn't hold any vacuum that I applied. So that means it never opened, and it was a vacuum leak.

[takza]

If it runs bad...then I'd say you are getting some exhaust gas all right. There were a few threads on passing emissions...3AC power had to.

Maybe check the air injection thing that comes off the air cleaner and goes to the exhaust? Do you have the air pump or should the car have it?


Here's a good link......

<a href='http://www.aircarecolorado.com/repair/toyota.htm' target='_blank'>http://www.aircarecolorado.com/repair/toyota.htm</a>


General stuff.......

"I do emissions testing where I work. If it failed on HC and CO, an oxygen sensor is a very good place to start. If CO is very high it will make NOX go down, because CO eats NOX. Now if you replace the sensor and some plugs and it fails yet again, but on NOX, check your EGR system and charcoal cannister, and if they are functioning then you may need the catylitic converter. Make sure the EGR is opening when you rev the engine. Just stick your finger on the diaphram and see if it moves. I hope this helps, and have a nice day...lol"

"My limited understanding is that more NOX is generated by higher temperatures.
The approach taken to reduce these temperatures has been since 1973
1 Retard the ignition
2 Retard valve timing
3 Add exhaust gas recirculation

Another alternative is to increase the amount of excess air.
A given amount of fuel will have to heat a larger mass of air.
The objective will still need to be to generate the same gas pressure on top of the piston. But the temperature required to do so will be less than that for a smaller amount of air. The lower temperature will result in less NOX"

[AbusedJalopy]

Thanks takza, I will try those. I found a place that sells installed cats for $85, but I'm not sure I want to spend that money if I don't have to, hard to tell if the fixes I have done are enough to lower the NOx enough to passing range. Thanks again.