The good folk over at the 'ancient' se-r-list.org site faithfully send a summary of the week's postings which I'm embarrassed to say is the way I usually keep up with the discussion. One of the threads had to do with passing emissions tests - some poor soul with a '91 was having a tough time. A fellow who signed himself Wayne posted this after a search of the history over at the list; while I suppose this could be put up at the general SR20 area, it should be germaine to those of us with ve's who live in smog test areas. For Atlanta, all I did with mine running a JWT ecu was pull the timing back from 15* to 10* and it JUST snipped by NOx (we have no egr on the ve). The rest of it was ridiculously clean. If I understand it correctly, NOx is ONLY an issue under the light loads of the OBD1 (sniffer & dyno rollers) test; if the test were at higher revs/greater load it wouldn't be a problem. (Cold 300wt in the gearbox oughta do it --
)
"Here's pertinent stuff I could find in my archives (nearly 13 years
of list messages) I never had any trouble with mine in Ohio, where
we had a tail-pipe sniffer on a dyno test. Once I even went in with
a golf tee obviously plugging my EGR and it passed
Sounds like it
could be a cat' or timing.
=====================
"Get a gallon of denatured alcohol at HD or Lowes and dump it in with
about 4-5 gallons of gas remaining in the tank. That usually does
the trick for me
and I've passed with some pretty wild set ups.
Alcohol *should* reduce your combustion temps enough to clear the NOx and
it will certainly reduce the HC's. I wouldn't go more than 25% and in
fact
recommend about 15-20% alcohol because your car will run lean with any
more and cause more problems than you solved.
=====================
HCs are closely related to the cat. Either your engine is dumping too much
fuel or the cat is just bad. Do they give ya a print out of what the HCs and
others look like ? Looking at CO readings U can determine if the feedback
system- O2, is working fine. If it stays somewhat close to linear sweep
across the line- but has small bumps up and down down that CO test... then
the O2 is working, if U see large spikes and it goes off the scale then the
O2 is failing and is not recovering in time which would cause the car to run
rich, and the HCs will be too high. Another thing I see alot is people go in
for a test with the car not fully warmed up. I like to go out drive it for
30 min HARD, and when waiting for my test I sit there holding the gas at
2500RPM and reving it up sometimes to keep the cat lit off and super hot to
make sure its operating at its full efficiency. If U can list some things
you have done to the car if anything ? like mods or tune up things ? If U
don't have a PAIR valve on the front of the engine- all 91-93s have it then
it will cause the HCs to go up and might not pass the test. I would start
off with a cap/rotor/wires/plugs. Make sure the timing is at 13deg when
going in for emissions ( put it back at 17 or 19 after the test )- it will
feel slow as hell but trust me I passed with flying colors with retarded
timing- it helps the NOx. Also run some injector cleaner through it- but
make sure when U do go in for a re-test that U have ran all the injector
cleaner out- fill the tank up dump the cleaner in the tank, drive it till
empty and run the 2nd tank to empty also. The injector cleaner will make the
car fail also if U drive in on that stuff. But the NOS injector cleaner
works really good- I swear by it. Then after that install a new fuel filter,
clean out the K&N or repleaced any dirty filters, do a oil change, get some
Redline MTL tranny fluid in the trans
Reground the MAF, and give it a
shot at the emissions place. Make sure the engine is fully warmed up and U
go around beatting on the car to warm the cat up. Even brand new cars will
fail the test if the cat is not warmed up.
Mike Jez
=====================
Timing should have little effect on your HC's.
High HC's are caused by having:
A) A mixture that is too rich,
B) Incomplete combustion, or
C) Ineffective emission control devices.
Situation A can be caused by: leaky or clogged injectors, clogged fuel
filter, bad fuel pressure regulator; misadjusted or bad throttle position
sensor (TPS), MAF or O2 sensor.
Situation B can be caused by faulty ignition items: Plugs, wires,
distributor cap or rotor, coil, etc.
Situation C is generally a bad catalytic converter or PAIR/AIV, but most of
the electronics in the injection system can also be considered emissions
control devices.
So, the first thing to do would be a tune-up, replacing anything that is old
or does not test out to FSM specs.
Checking your O2 sensor is a must in this situation.
If everything else checks out, this would point to a bad CAT, but make sure
_everything else_ has been checked out first.
If your engine has been running rich for a while, this could increase the
chances that your EGR/BPT has gotten carbon fouled, but if you just tested
fine for NOx, then that system should be fine. The EGR/BPT system has no
effect on HC emissions.
Tim Rogers"
