What aspects of my tune would you say relate to what you see here? What should I adjust?

 

Update:

Fuel: I just remembered that when I changed my fuel pump a month ago, my fuel pressure went from 11 to 13 and I never told the computer about it. I hooked up and examined the car (as it was when it was smogged) and saw that BLMs were down around 112 consistently.

My Solution: I dropped BPC from 135 to 126. Drove around and the BLMs seemed quite happy, staying between 123 and 130 the whole time and spending a lot of time right at 128.

Closed Loop: I also had a hunch that the car was not going into closed loop for part of the test, because when I would take it out sometimes it would take 5 minutes of good warmed up city driving before it would go in, even though all other qualifiers were met.

My Solution: I narrowed the 02 "go in" thresholds and now when I putt around it goes into closed loop within 30 seconds if its warm enough. Any problems with this?

Timing: I took a peek at a stock 350 TBI timing table given to me, titled "F_AXKS". My self tuned tables were running anywhere from 6-12 degrees MORE timing than this table, ESPECIALLY in the lower speed areas! So I swapped this table in completely.

My Solution: I swapped in the table with the significantly lower values. Car runs a bit doggish now, but I think that may help out with my NOx values.


I can't re-test until Monday. Opinions on the changes I have made based upon my emissions readings?

 

Did you happen to data log during the test? If so check to see if the EGR was active during the 15 MPH portion of the test. If the EGR wasn't active that will cause the high NO reading. Which was well within specs in the 25 MPH test.

What puzzles me a little is the CO and O2 readings. They contradict each other as at that CO% the O2 should be lower. Or, at that O2 the CO% should be lower.

It maybe a slight misfire causing the O2, CO & HC readings.

RBob.

 

Not being in closed loop will cause high HC values. The cat requires the oscillating AFR to work. No problem narrowing the 'go into closed' loop values. As long as it isn't so far that an un-active O2 sensor allows it to go closed loop.

The cali calibrations run less timing and a richer AFR (via the o2 window) then do the fed calibrations. This reduces the NO and the HC.

The other item that always helps is to change the oil & filter before the test.

RBob.

 

it looks like you were a little on the rich side.
leaning it out can raise NOx because the extra fuel helps to cool combustion chamber temps.
pulling some timing should help with the NOx & also with the HC a little.
the changes you made should help, but only after the retest will you know if they were enough, or too much.
the only other thing i can think of is to make sure your EGR is working under the test conditions.
good luck

 

My EGR comes on rather easily, 4% TPS so I'm sure it's on throughout the test. Driving around it pretty much is on anytime I am moving, even 4mph.

I also tested the EGR by closing the diaphragm at idle, killing the engine. I can also see it close when I crank open the throttle a bit at idle. Seems to be working.

The car runs at a constant 86*C which is VERY reasonable (185*F) for a 3rd gen car so I don't think heat is a problem with the NOx, I'm betting it was my timing tables which were outrageous compared to that stock Cali calibration I looked at. Can too little timing mess up emissions?

Not sure about the possible miss fire, I wouldn't say it runs smooth as glass but it runs good. Wouldn't my numbers be significantly worse if it was really misfiring?

The CO reading the guy said was an indicator that my "rich/lean" is having trouble, which points to no closed loop. You all agree with him on that? He was pretty vague like maybe he didn't know what he was talking about.

 

No closed loop, maybe (but CO less than 1% means it's probably ON), but your cat is probably dead (or has very little life left).

But, yeah, reducing the spark timing by 10 degrees usually works, and is cheaper than a cat, as long as you have the means to program that. The late burn will help HC, and help get the cat hotter to help CO, and reduce NOx.

If it were me, I'd be looking for a new cat. It'll really help the smell. From the fairly low HC, I think it's not really misfiring, so a new cat should survive.

 

The cat is only about a year old. However it did see quite a few months of pure open loop daily driving while I tried to get my tune in order. Think I might have fried it? My cousin has a muffler shop so no big deal to replace it if need be.

 

Just realized something - my AIR system is electronically disabled, but it's hooked up to the smog pump and headers and everything. Could the lack of an electronic signal cause the air pump to be pumping air into the headers all the time throwing off the sniffer reading as well as my 02 sensor reading? Or will lack of power to the diverter valve just direct air to the atmosphere?

 

On my 90, if both solenoids are de-energized, the air from the pump is vented to the atmosphere.