Thrak

1985 - sat for 5yrs before I got ahold of it... its running really good (sotp) but...

First failure gave these numbers:
HC - 134 (allowed 152) and 134 (157)
CO% - 1.80 (0.97) and 1.95 (0.88)
NOx - 421 (1082) and 568 (1184)




Then, replaced upper and lower runner gaskets, throttle body gasket, upper and lower injector o-rings + replaced injectors (from an 86)... new wires, plugs, o2 sensor, drained/cleaned/flushed cooling system... cleared the computer and put about 100+mi on it...


Test results from today:
HC - 103 (152) and 133 (157)
CO% - 1.55 (0.97) and 1.73 (0.88)
NOx - 483 (1082) and 649 (1184)


CO% went down, but not hardly enough to make it pass... the other stuff is fine it seems...

What else can I check? I'm thinking maybe timing and fuel pressure?? Other than that, unless the o2 is bad, I'm lost.

CFI-EFI

It is still running rich. The HCs tell you that you are burning most of the fuel, but the CO tells you the mixture is still too rich. When you lean it out the NOx will likely jump, but you have plenty of head room, there.

RACE ON!!!

Thrak

Thats what I figured, but I dont know how to lean it out... isnt it all controlled by the ecu?

toptechx6

As CFI-EFI said it is still rich, I would check the 86 injector flow rate to be sure it is the same as your 85, and checking the fuel pressure won't hurt but would be unusual to be high unless you have made changes. Could be a weak CAT too, best of luck.

Thrak

funny thing is, I'm pretty sure the injectors flow less... I havent adjusted the fuel pressure at all...

<-- confused

toptechx6

Another possibility is running too cool, is your T-stat stock or low temp?

Thrak

thats not it... when its on the rack being testing the temp is really high... like 220-225... fans running and all...

toptechx6

You're right, that sounds like it is getting warm enough, the CAT is still a possibility. Sometimes checking inlet and outlet temps will tell you if it's working but not always, wish I had another suggestion.

SunCr

Whomever has worked on it needs to scan it. If it's Rich or Lean, that will point to the solution. If it's perfect, the CAT is bad.

Thrak

we shoved a wideband sensor far up the tail pipe and it was reading pretty good... ~15.1 @ idle and it never really bad when we free revved it either...

before all the repairs we did, it was off the scale lean (over 21:1) at idle, so I know the repairs made a big difference...

I guess that cat is bad... thats the only thing left really...

I always thought if the cat was bad, all the emissions would be way off, but I guess not...

toptechx6

HC will usually only climb if you have a misfire, newer CATS are 3 way and control NOX somewhat but I'm not sure older ones do. As CFI-EFI indicated too, high CO will lower NOX, that could be why it is okay.

CFI-EFI

Very interesting. My results are in red.

My '84 passes my test and yours, with the exception of your high speed CO standards. And even then my high speed CO is substantially lower than yours. Normally, a reaction would be..."So what!" The difference is, my car has NO cats. If I were you, I'd start looking for false air and vacuum leaks. Good luck.

RACE ON!!!

Thrak

thats weird...so, my numbers are higher than a car w/ no cat lol... if my cat wasnt working at all, I'd expect numbers like yours.. which I have, right?

*sigh*

I dont know where else to check for air... I'm about at my limit...

toptechx6

Don't get too confused, that cats are there for a reason. If they weren't required at all manufacturers would not spend billions installing them.

CFI-EFI

I'm not saying that cats aren't effective. What I AM pointing out, is that your numbers can be much better, even if your cat is bad. I have a pretty good idea where MY high CO numbers come from. As an illustration, I have a 1978 GMC 3/4 ton pick up with a 400 CID, Quadrajet 4 bbl engine. The GVW of the truck is over 7500 pounds, so it has, "heavy duty emissions". That means that it has no EGR, no smog pump, and no cat. Of course it has no O2 sensor and no computer. The standards it must meet to pass are:

HC: 1200, 1200
CO: 5.00, 5.00
NOx: Not regulated


Test results:

HC: 71, 117
CO: .92, .71
NOx: Not tested

That dirty old truck not only passes the test for my '84, it passes your test, too.

RACE ON!!!

MikeC4

have you checked your initial timing at idle? A good starting point would be somewhere in the vacinity of 10 to 14degrees BTDC.

toptechx6

I would never suggest replacing a cat as a cure all for an emmision problem, quite the opposite actually, it would be a last resort after exhausting all other possibilities, no pun intended.
One other thought on the above failure would be to check the air injection. Seeing some engine data would help too if you have it.

CTYANK2

Well at least the emission standards there are reasonable. Limits here in Connecticut are:

HC: 0.88
CO: 0.28
Nox: 614

Thrak

We're going to check timing first.. then try to get some data.. even though we're new at this whole data thing.

I'd rather not replace that cat, so I am going to try all other options first.


I'll be making my way to the Scan & Tune section shortly.


Any and all suggestions are welcome!!

CFI-EFI

In my state, at least, the standards vary with the year of the car. That is why the standard for the '78, HD, truck are so much higher than the '84, car. The standards for for an '85, here, may be the sames as Thrak has to meet. Second, it is pretty obvious that your standards, at least the HCs, are expressed in different units of measure (grams per mile?). The HCs we are discussing are in parts per million (ppm). The CO is stated as a percentage (%) of all the exhaust gases. I don't know what the units of measure of Thrak's NOx standards.

RACE ON!!!