Failed Emissions, High NOx

[anubix]

Failed my CA emissions test.
NOx is too high.

89 LXi sedan, manual trans

The emissions test is done with the vehicle on a dyno at 15mph and 25mph.
When I put a vacuum gauge on the egr (at speed) it pulls ~3-5" of vacuum.

As soon as the car hits 15 mph in 1st gear, EGR closes: 0" of vacuum.
As soon as the car hits 25 mph in 2nd gear, EGR closes: 0" of vacuum.

The engine does stutter when I put a vacuum on the egr while idling. EGR valve is working.
The book says the ecu activates the EGR (via solenoid in the magic box) in accordance with data it reads from the map sensor, tdc/crank sensor, cyl sensor, tw sensor, and throttle angle sensor.

Anyone seen this before?
Any advice on a procedure from here?

Stuck.

[Brennan]

Just had to deal with the same problem not a year ago on mine (89 LX-i M/T). I believe if you stick a vacuum on it, the engine should die if the EGR ports are clear (though, I'm not 100% on this). I remember my mechanic checked if the EGR ports were blocked with this method. He did so and mine immediately stalled.

This isn't the most technical reply you'll get, but if you just want to pass emissions try a bottle of Guaranteed to Pass (http://www.amazon.com/CRC-05063-Guaranteed-Emissions-Formula/dp/B000CIPUR8). It's about $12 at VatoZone; dump it in a full tank of gas, drive around till empty, refill, pass emissions. I'm not usually one to treat the symptoms and not the cause, but I passed after using this product! Just a thought, you may want to give it a try. :)

[Dr_Snooz]

EGR valve is working.

NOT working! Engine should stall. Pull the valve, check for carbon buildup and valve operation. You may need to clear the channels too: https://www.youtube.com/watch?v=d8N-SE047VY. High NOx is almost always EGR, so good job looking there first. It sounds like you are working through the troubleshooting section in the manual too, which is always wise.

What were your numbers, BTW?

[anubix]

OKAY:
First I was mistaken, the entire test is done in 2nd gear. ~1700 RPM @ 15mph, then ~2850 RPM @ 25mph.

Removed EGR and ran a mess of Brake Parts Cleaner into the port that's past the valve into the intake.
Don't think there was any blockage: but if there was, there's surely less now.

re-Installed EGR, warmed up engine: vacuum pump now on egr now kills engine like it should.

replaced magic-box of vacuum spaghetti & emissions mystery.

Symptoms persist (verified on smog-machine)
EGR is closing at medium rmp (~3000) when it should remain open.

What I meant when I said EGR is working is: while accelerating but before reaching desired emission-test speeds the EGR valve receives up to 5" of vacuum. It is not working right, but it IS working. Everything that needs to happen to give it vacuum is happening.... just not at ~3000 rpm during the emissions test.

Numbers: http://imagebin.org/240555

I can obviously see whats occurring to cause the high NOx condition.
Question still remains: what sensor(s) malfunctioning would create this scenario?
Since I'm still fumbling around like a virgin in the dark: I will try swapping ECU next.

[Dr_Snooz]

I'm inclined to think you're going to be replacing the valve itself. If you aren't running through the troubleshooting procedure in the manual, then do so. It will give you all the specs and everything else that you should be seeing. Check the operation of the EGR valve itself to see if it's hanging up anywhere in its range of travel. Was there any coke build up that you could see when you had it removed?

[anubix]

I'm inclined to think you're going to be replacing the valve itself. If you aren't running through the troubleshooting procedure in the manual, then do so. It will give you all the specs and everything else that you should be seeing. Check the operation of the EGR valve itself to see if it's hanging up anywhere in its range of travel. Was there any coke build up that you could see when you had it removed?

Replacing EGR valve was the first thing I tried.
EGR valve was cleaner on the intake side than exhaust side but did not see any blockage on the passageway in the valve (or intake): and the diaphram did move through its entire stroke without impediment, and also holds vacuum when applied with hand pump.
Different EGR changes nothing.

I will run through the troubleshooting steps shortly, however I don't believe it will shed light on my problem.

[Dr_Snooz]

You aren't going to see anything in the channels. You'll have to drill them open to see the buildup. If everything you could see was sparkling clean, though, then it's not likely they are the problem.

Check your timing. What are your coolant temps running? What grade of gas do you use? Check for vacuum leaks. How old is the cat?

[Dr_Snooz]

How many miles on the engine? Have you done an Italian tune up yet?