EGR VSV and Vacuum issues

Yeah you're telling me. I've seen some stuff online saying that Toyota has a tough time testing the EGR because it uses exhaust back-pressure to make sure it only operates when driving. So a dyno based smog tested is usually the only sure method of verifying it. Not sure how true it is on 1st gens though.

 

This sheet shows the measurements at idle and they are good, they all pass. Is it the test under load that it failed on the egr test numbers?
I think at idle you should be able to pinch off the vacuum line going to egr at idle and the engine not die. And then under load when that line is pinched closed it should die... Or something similar. Crap, I dont remember it's been a few years but it's nice, I can tell you at least know what you're doing so makes it alot easier to talk fixes and crap. So that's a good thing lol

 

Trust me it's been my obsession to fix this for the past two weeks. I could probably design an EGR system at this point.

 

I decided to hook up a vacuum line and run it I to my cab as I drive around. It acted as my EGR in a sense. Well I see vacuum just fine under engine load. So I suspect I need to let the smog guys know the EGR will only work when driving.

 

The "smog guys" will run an engine ready test. Beat em to it and take it in when you get a green light after running your own ready test.

 

Yes, I was thinking the VSV maybe should be activated when EGR is off, so on at idle or with key ON.

EGR valve should open some during regular cruising I believe. By mixing inert exhaust gases with the air/fuel it slows the combustion down, lowers the pesk combustion temperature which reduces NOx emissions. You test don't show NOx, do not sure it's a problem.

To test just the EGR valve you apply vacuum using a hand vacuum pump directly to it at idle and the engine should stumble and die. If it doesn't either the valve is bad (broken diaphragm [would not hold vacuum] or stuck) or the EGR pipe is clogged. Like someone mentioned the EGR valve itself rarely goes bad. Usually it's the modulator, VSV or clogged pipes that cause a problem.

Did you clear the codes or disconnect the battery shortly before getting the test, like within 100 driving miles? I wonder if they just based the fail on the readiness monitor being incomplete.

 

I cleared the codes after the test yes after checking the codes. The code I pulled wasn't even for EGR, and every emissions monitor is ready except the O2 system. But there are 3 different drive cycles to set that one to I don't expect to have that one ready. At least in CA we can have one unset and still pass smog so wish me luck today.

 

Just wanted to update this thread for anyone else who may be looking into EGR function in the future. I have confirmed everything is working as it should. The VSV should click open when you turn the truck to on and when at idle. This will prevent vacuum from building in the lines and opening EGR at idle or WOT. Under the right conditions the VSV is pulsed closed and you can confirm it by following this important step in the FSM (which I hadn't noticed before starting this thread).



I did not notice that I needed to plug the vacuum line running from the VSV back to the throttle body. This was preventing vacuum from building and making me think there might be a faulty VSV.

Lesson of the day is read the FSM carefully and do as it says.