High Nox smog results...HELP?

[Griswald]

Ok, here we go,
I recently bought an 89 Mustang 5.0, 5-speed, and everything was original, EVERYTHING.

My first results were
15mph
HC max=85
measured=122

NO max=565
measured=1191

25mph
HC max=67
measured=70

NO max=522
measured=691

I read around, learned a ton about the car, and changed a few things.
I installed new ACCEL distributor+coil, Autolite 25 plugs, Ford wires, IAC, coolant temp sensor, air charge sensor, O2 sensors, PCV valve-filter-rubber grommet, air filter, fuel filter, and had 2 new cats welded on (bigger set after the H).
Cleaned the EGR valve, thermactor tube behind the heads, TB, and EGR spacer. Then fresh oil and filter.
Set timing at 10*, did base idle reset, and set TPS at .96.

Took it in yesterday,
15mph
HC measured =50
NO measured= 637

So I went from 1191 to 637 with all that, but I'm still a measly 72 parts per ****ing million shy!!!

Well today, I shot myself in the foot. This morning, I backed the timing down to about 7-8*, then went back to the smog shop.
At 15mph, this lowered the HC by 15, but raised the NOx by 552! I'm so damn confused now. Anybody have any good ideas (legal or not) on how to achieve my goal?
Thanks,
Chris

 

[seijirou]

High NOx is due to combustion chamber temperatures being too high.
I'm going to assume that your engine isn't running hot or you'd be complaining about that too.

Because you're also getting more HC than you should, my initial suspicion is that you have a lean condition causing both high combustion chamber temperatures and an incomplete burn.

I would clean the MAF hot wire pair in the MAF, there is a spray cleaner you can get for job specifically. Brake cleaner works too. Don't try to physically wipe the wires with anything or you may break them. Also don't spray them for a couple minutes if after the ignition has been on. Crap buildup on them will insulate them from the incoming air, causing you to run lean. This is more common if you use an oiled air filter like K&N.

Make sure you don't have a vacuum line connected to the barometric pressure sensor.

Check for vacuum leaks. Check your fuel pressure. Check your compression and see if any cylinders are abnormally high indicating carbon buildup. High compression = high heat. Do some searching on running lean and see how other people dealt with the problem because I'm sure I'm forgetting things.

Also if you tried to cheat with some alcohol in the tank, burn it all out and use regular gas as alcohol will make you run lean.

 

[Griswald]

Thanks man! Fuel pressure is at 40 with key on, and around 33 at idle. Cylinder balance test is good, and I have codes 41 & 91.
I have found an abundance of information on this site, but need to go through my bookmarks now to put it in order. I threw up the original post yesterday out of frustration, hoping for a magical answer, but I know what I need to do. I've never opened up a computer to check pins for voltage, done a compression test, or gone on a vacuum leak hunt before. First for time for everything I guess.
Oh, and I've never had a car fail smog either.
THING THAT BOTHERS ME THE MOST, IS IT RUNS GREAT!

 

[Mustang5L5]

Code 41 and 91 are o2 sensor indicates lean codes

http://www.stangnet.com/mustang-forums/573573-koer-code-41-a.html

This could be why your nox is high. Could possibly be bad o2 sensors or another cause

 

[bp50]

This is a shot in the dark, did you reset the ecu after doing the tune up? maybe the computer hasn't adjusted to all the recent changes.
peace.

 

[Griswald]

I've unplugged the battery numerous times during all the changes, but I don't know if I have to drive it around a minimum amount? I've only taken short trips around the neighborhood because it's not registered or insured.

The O2 sensors are new.

 

[Mustang5L5]

Then there is another cause as to why you are running Lean that you need to troubleshoot.

 

[Griswald]

I'm going to check continuity of hego ground to computer (pin 49 I think), then check voltage at idle. If those are good, then EGR vac, and EVR voltage. If that's good, then I'm taking this whole damn thing apart!

 

[Griswald]

Well after driving a little bit, I finally threw a KOEO code 34. KOER is still 41 & 91, but this 34 is new.

 

[Mustang5L5]

Egr code

Here is some info to help troubleshoot.

http://www.stangnet.com/mustang-forums/783241-code-34-41-91-any-guesses.html#post7882070

 

[Griswald]

Thanks for the link!