rsscoty

I just got back from the emissions station,my HC is still high. The guy at autozone told me it is probably burning rich.. how would I find out. it is the 305 with TBI.
Thanks Scot

five7kid

iTrader: (14)

List all the readings they gave you on the printout.

Also, your modifications/settings/recent maintainance would be helpful.

rsscoty

HC 1.8572 allowed; .8
CO 7.7715 15.
NOx .0016 2.

Open element breather
was running quite a bit of Heet during test
According to the Supplemnetal Diagnostic Info sheet they gave me:

Ignition misfire, fuel distribution problems, grossly advanced timing, and/or mchanically induced misfire
I haven't done any mods except for the open element breather. I run regular unleaded gas.
Thanks Scot

RB83L69

You need a new cat. Not the kind that meows.

patrickm00

before you do that just yet, see how it does if you retard the timing a couple degrees or change the O2 sensor. both of those should be cheaper jobs, and may fix the root of the problem.

rsscoty

will a catco be sufficient or should I get a stock one. I currently have the stock exhaust, but am going to a flowmaster 80 series three in pipes and a set of headers soon

RB83L69

The Catco should be fine.

Looks to me like the engine is running right but the cat isn't cleaning up the last little bit. I wouldn't mess with the timing becasue it doesn't just jump out of tolerance all by itself. If the O2 sensor was bad such that it was telling the ECM that the exhaust is lean, the ECM would richen it up, but that would result in high HC too. If both of those were way high, then the sensor would be suspect.

If you're planning on changing the exhaust, I'd suggest doing it now and getting the right size cat for that, otherwise you'll just have to buy another one of the larger size when you do the exhaust upgrades.

CrispyClutch

Yeah retards have bad timing.

patrickm00

sorry, i originally misread your chart, i thought HC .8 was "allowed" and 1.8 was the reading, etc. yeah, cleaning up NOx and CO's is mostly the cat's job. though i wouldn't rule out running pretty lean, or less likely, overly advanced timing.

timing shouldn't go out of spec on its own, but some people we buy these cars from are real idiots, so i have had to adjust it on my first run through emissions before.

Vader

That WAS supposed to be an attempt at humor, right? Defaming other members isn't humorous, but I'm guessing it was intended as humor, not an insult.

five7kid

iTrader: (14)

Hmmm, I've always seen allowables given in round-ish numbers, and actuals to a few decimal places.

If that assumption is correct, then you indeed are running rich. Since the NOx is low, I tend to believe that even more (if NOx was high, I'd go along with the cat diagnosis).

O2 sensor, plugs, perhaps wires/cap/rotor. If it has been running rich for a while, then a new cat may also be required (running rich, especially a misfire, will cook out a cat).

I'm no TBI expert, but I believe there is an air inlet temp sensor in the factory air cleaner, right? Did you transfer that over to your open element?

rsscoty

Yes I kept the air inlet sensor.I know I'm in need of a good tune up, plugs, wires cap, rotor..the whole nine yards. I have also been contemplating going on ahead and replacing the O2 sensor.

Guess I will do those things then worry about the cat later. I want to go to a 3 in exhaust and headers but need to wait a few months before I do the whole exhaust. If I change the cat now, I would just have to buy another one in a few months, so I want to avoid that if I can.
Thanks for all the input guys