Dewey316

while, in the ongoing struggle to pass the sniffer...

the last couple of days i have gone to DEQ, i start honing in on the numbers to pass, and after 3-4 tries, my HC's shoot through the roof. at first i thought that it was me making a bad change, but this week, i went right back to the BIN that was close the try before, HC's were still very high, no matter what i changed from that point, the readings didn't change. could this be something in the computer that might cause it to do this, or should i be looking for some sort of mechanical issues (ignition is all new, new coil, new wires, new plugs, new cap/rotor) i have gotten VERY close to passing, and actualy did pass the test once, but failed for being above the noise limit on that run. since then i cannot pass, i have even put the stock cam back in, and run the stock chip (or what i think is the stocker, my stock chip is lost, so i downloaded a bin, but i have nothing to compare it to. still no luck passing.

RBob

iTrader: (1)

Can you post all of the numbers and the conditions the test were made (MPH, RPM, load. . .), and a little about the engine modifications.

When you say 3-4 tries then HC's shoot up, are these in a row. IE: one run after another?

RBob.

dimented24x7

iTrader: (2)

Might seem stupid, but whats teh condition of the 02 and the cat? Just about any cat can be plugged by carbon deposites if the tune inst right. Had it happen to my truck after the CPI injector bit the dust. Came back to life w/ a new injector and O2.

dimented24x7

iTrader: (2)

You could also try reinstalling the air if its off. My friend got some really low numbers with the AIR on a cammed Vette L98.

Dewey316

ok. first off, Rbob, we do a chassis dyno test, the load and RPM vary. since i am TBI, i can post a datalog, but as you know at 160baud, it will be missing alot. i can tell you the BLM readings are good, if i go to open-loop the o2 values vary but never go about .450

cat is less than a year old, air is hooked up. the motor as i tested last week is STOCK, as in, all the mods came off. all the emisions equipment is intacked. it is on a fresh oil change, with new ingitions parts. the o2 has less than 1k miles on it. i have tried with both the old, and new o2, it makes no diffrence.

and Rbob, yes they are back to back to back runs. in Oregon we can keep going around until we pass, there is no limit, and no charge to test.

RBob

iTrader: (1)

Hmm, is this a test where the operator gets to drive the car, and if at any time a limit is exceeded it fails? If so, do you have a print out the test over time?

Other wise do you have all of the emission levels your car tested at (HC, Co, Co2, NOX)?

Sometimes one can be traded for the other. And knowing the others can help explain why another one is off.

The HC's just shooting up after a while doesn't make sense. Something is going on. I wonder if maybe something such as the forced knock test is being invoked. Or, do you think the go-pedal is being depessed enough to go into PE mode?

Do they have a large fan in front of the car to keep it cool?

RBob.

Dewey316

i have a print out, but it is useless, the HCs are a line across the top.

the HC limit is 1.2ppm, i was down in th 1.9ppm area when is tarted, when this happened it jumped to 24ppm. the NOx was a hair high. the limit there is 3.3, i was in the 3.6-3.8 range, when this happens, NOX drops to almost nothing (.6).

CO levels are in range no matter what, the limit is 30, i test very low on these.

Co2 is not tested.

no PE mode, i have disabled that, and the pump shot, it makes no diffrence. and once the HC's jumped, i put the last chip back in (i have 3 chips i burn , so i always have the last 2 configs handy) and the HC stayed up. i have the fan on a switch in the car, temp seems to have little effect. i have run everywhere from 160* - 230* same issues, after a few runs, the HCs peg, and i just head home for the day.

Grumpy

How old is the oil?.
The PCV can draw alot of what becomes HC fumes thru it.

180dF Thermostat.
210dF fan on

Too lean will drive HCs high.

A year old on a HiPo car, and I'd bet the cat is about dead. It doesn't take long, to kill a cat, at a WOT that makes HP. The newer stuff all has code to deal with converter life at WOT.

Dewey316

Grumpy, what has me baffled, is that i am close, and hten all of the sudden, the HCs spike. no matter what i do, i have sat in line with the Tach reading 5k, to try to keep the cat warm, or i can sit at idle, once i get the run with the spike, i can't get that level back down.

any other nice tricks that people know would be helpful..

with the cam in the car, i ran 25% denatured alchohol, had the fuel trimmed down so far, it would hardly run, disabled pump shot and PE, had to make my max TF steps down to 5, set idle to 1100, and backed the timing off 4*, it was still failling for HC's

RBob

iTrader: (1)

With the HC & NOX a tad high and the CO very low, I would back off the timing. Remove 2 - 4 degrees across the board. Easiest would be to just twist the distributor (w/a light) or up the inital timing in the bin by the 2-4 degrees.

Check your data log IAT temperature. See if it starts to increase about the same time the HC's skyrocket. Many TBI cals add a bunch of fuel when the IAT goes up in order to cool the motor and ward off detonation.

Another thing to try is a stock calibration for a '92 f-body (The newer the better).

RBob.

Twilightoptics

Weirdest thing is passing with the aftermarket camshaft.... (failed for noise).... but not getting as close with the stock cam.

dimented24x7

iTrader: (2)

I just remembered seeing this. In the 8746, as well as in mine, there appears to be a mistake with the code that controls the smog pump. Looks like they used the wrong rpm value for the max allowed speed for the smog pump to be on. They used the rpm/25 value for the 7747 instead of the rpm/25 value for the 8746. In the 8746, that addr stores the scaled rpms. Only remembered this because if it is indeed a mistake, the smog pump stuff is practially worthless because the airflow to the cat will shutoff and the air diverted after the engine passes 2000 rpm. Dont quote me on this, though, im not an expert. But, keep this in mind that above 2000 rpms, there is a possibility that your airflow to the cat is shut down. Could cause HC spikes when the rpms pass 2000 rpm on the dyno.


Edit: Made a mistake in the post

If you want to fix it, go to D49E in the prom and enter something like 224 = 4000 rpm. That should ensure the air stays on during the test, assuming im right and not off in left field somewhere.

anesthes

iTrader: (12)

Is the car a manual by any chance?

-- Joe

Dewey316

yes sir.

anesthes

iTrader: (12)

Thats why then. WHen you shift the HC's go high. You need to shift quicker on the dyno.

We had similar problems here doing tests.

-- Joe

Dewey316

if only i could drive on the test

3.8TransAM

Possible IAC issue with it closing to soon instead of hanging open a tad bit to burn that slug of fuel?????????


maybe?

LAter
Jeremy

Dewey316

dropping my TF counts helped HC emisions.

dimented24x7

iTrader: (2)

Id set the car back to its normal settings and take it out on the road and drive it for awhile and then test the temp of the cat. If you know someone with a pointable thermometer then you can measure the temp of the cat compaired to the rest of the exaust. I would imagine the cat would be around 800+ deg. F after a good drive, and not the same temp as the rest of the exaust. I would think a shop could perform the test to make sure the cat is good. Thats the first thing I would look at if I couldnt get the HCs down. Definatly worth while to make sure its not dead rather then assume it still works...

Twilightoptics

With a hot cat and a Pyrometer... I've only been able to attain 300ºF before the cat, 400ºF after the cat.

An emission specialist said that was the perfect reading for a cat working properly.

dimented24x7

iTrader: (2)

hmmm... runs alot cooler then I thought it did.