Co is high - NOx is low

There is some true to this. CO is generly formed form incomplet combustion which is usually the the result or occurs durring lower combustion temps which reduces NOx formation. As you raise peak combustion temps and pressure you generally increase NOx as well so it is a bit of a balancing act. EGR reduces peak temps and NOx too.

----------------- TheSnoMan.com

Figure out why it is over fueling.

Yes.

Excessive CO can be caused by other things as well. Over fueling is not the lone cause. Basically it is from incomplete combustion and there can be several causes for that with excessive fuel being but one of them.

----------------- TheSnoMan.com

Incomplete combustion because there is not enough air for the amount of fuel in the combustion chamber, which is just a fancy way of saying "over fueled."

So, offer up the others of the several causes. You're here to help, right?

Not really. CO is because it is on completly burned properly not just becuse the A/F ratio was wrong

It could be timing, low compression, bad EGR valve, plugs fouling, low compression resulting in a poor burn, higher oil consumption which slows burn and can add CO to name a few on top of a over rich mixture and a overly lean one which can cause higher CO too. The fact the NOx is low shows the combustion temps are low and likey not burning properly since NOx is a direct result of combustion temps and pressures.

----------------- TheSnoMan.com

Horse droppings. CO increase is documented as being caused by insufficient air for the amount of fuel.

Indirect cause. (if even that)

Nope.

Sure, if it raises manifold pressure enough to cause power enrichment, IOWs an indirect cause.

Nope. CO drops when a plug miss fires. No fire, no CO.

Malarky.

Motor oil falls into the 'over fueled' category.

Naming them doesn't make it true.

Not on this planet. A company with the resources of say Toyota would certainly know more about it than you;

The charts on pages 1 and 2 clearly show how air fuel ratio effects CO levels. Page 4 shows likely causes of excessive CO, notice how most of your so called causes for the high CO aren't listed. :-) Note, the charts on pages 1 and 2 are pretty much an industry standard and have been for quite a long time. They'd be found in the documentation that comes with most if not all 2, 3, 4 and 5 gas analyzers, they are found in training materials from GM, Ford, Chrysler and of course Toyota. They are acknowledged and used in the emissions testing industry by the vendors who conduct the tests and as part of their technician outreach programs. And finally, there is a man named Brettschneider who says you are full of shidt.

Without knowing what the pre-cat NOx levels are, you are just guessing.

Thanks for all the ideas - I should mention that despite these readings this S10 starts up in zero degree weather in less then a 3 second crank which is why I like to keep it around for winter driving - so I always thoguht that it was properly tuned....

Maybe in your "horse dropping"

----------------- TheSnoMan.com

YOur real lack of knowledge really shows through here as you suggest that rich fuel mixtures are the only cause of this problem. Granted it can be a cause but far from the only cause!

I love this, again your lack of wisdom and understanding on this subject is shining through!

Agian you are so clueless because low or unbalnce compress can cause incomplete buns and you would know that if you had any real knowledge on the matter.

Again wrong on your concept. If there is enough EGR to delute incoming mixture regardless of manifold pressure it will remove availble oxygen for mixture and result in higher CO emissions.

I love this one, the unburnt fuel just disappears and does not partically afterburn in exhaust huh. Again you lack of knowledge shins bright like a beacon

The malarky her is you as usual

Trying to CYA on over rich huh? Not realy because though it is a fuel it has different octane and burning properties so it is no lumped in with "over fueled"

You mean you discounting them does not make them true right? YOu should not be giving advise on things you do not understand ALL aspects of

Your realy are clueless huh? A overlean mixture will not burn properly and BTW a over rich will also generally show high HC's as well while a normal mixture that has high CO for some of the other reasons I mentioned may have normal of near normal HC's

Post all the links you want it just shows that you really do not know and you look stuff up when you are in a bind.

Again you are complete wrong to assume that over rich is the only cause of high CO. it is but one cause and all of the tests you quote are likely on perfect engines in lab conditions not realworld ones with wear and age on them that are no longer up to full spec.

No, I am not guessing, you are. The CAT removes a percentage on them not a fixed amount and the low reading clearly shows that combustion temps are likely low because as stated earlier that has a direct bearing on NOx production which you would know if you really had a clue.

----------------- TheSnoMan.com

Blojob, you are right on every point. Everyone but you is clueless and makes guesses in place of factual statements. I think they act this way to feel better about themselves. Keep up the quality, factual info. Your input is appreciated here. Heck, I search for your posts every day now. Thanks for pointing out that some of our best mechanics in the repair industry are really just ignorant frauds.

Toyota MDT in MO

From the Department of Redundancy Department?

Looks like you have a bunch of studying to do.

Love anything you want, still doesn't change the facts.

That would produce a miss fire and there would be high HC as evidence.

Concept? It's proven science. On MAF engines, EGR does NOT change the air fuel ratio, on speed density engines, the EGR changes the air fuel ratio because it directly effects the manifold pressure and the device reading it.

EGR "removes available oxygen?" Pure Snojob magic.

Any *professional* mechanic can access the writings of Paul Baltusis (Ford Motor Company) and Robert Schrader (Bridge Analyzers) and find that you are 100% wrong.

Unburned fuel shows up as HC, not CO. BTW, fuel is not "burnt" it is 'burned' (as if we needed yet another example of your intellectual prowess)

Why would a slow burn add CO?

Nope, just showing where you are wrong.

It certainly is.

And you -do- understand all aspects? I find that hard to believe given the number of and history of making grand blunders you are noted for.

Results in high HC and lowered CO.

Grossly over rich will show high HC in addition to high CO.

"Normal mixture that has high CO?" What sort of nonsense is that?

And they said the Dinosaurs were extinct.

It's called a reference that supports what I've been saying you blithering moron. Too bad, tough shit, you lose.

If I am completely wrong, so is the entire automobile industry along with all of the manufacturers of support and diagnostic equipment, the states of Arizona, Ohio, New York, Pennsylvania, Colorado, Wisconsin and California being as those are the states I worked with 11 years ago when I was employed by the worlds largest emissions testing company. But you know, I just can;t see the ranting of one little bozo with a snow plow trumping all of those highly educated people.

It's basic combustion chemistry you dolt. Matters not how worn they are.

How can you NOT be guessing if you are NOT testing?

So what?

Uh-huh... High CO and low NOx are never EVER caused by over fueling, even though that is exactly what is shown in the 4 gas chart referenced earlier, i.e., on the rich side of stoichiometric. Apparently you would rather ignore the evidence as presented and guess at the cause, which pretty much proves that any test results over and above hitting something with a hammer is totally lost on you.

No wonder you can't get your truck to run correctly unless you jack the adjustments. (which is a whole different subject of hypocrisy)

I snickered several places in the above paragraphs but this one got me to blow snot!!! LMFAO!!!!!!

Denny

I've stayed away from this post until now because I'm not a professional mechanic, nor do I own an S10, therefore I don't know how to tune your engine and I thought someone with more experience would point you in the right direction - which I think the over fueling remark was meant as.

It's my understanding that the NOx and CO emission from an IC engine are inversely proportional, that is, as you tune the engine to reduce NOx, the CO will increase and vise-a-versa. I also noticed from your OP that while the CO is slightly over limit, the NOx is much below the limit.

Therefore, I would start with a basic tune-up including: Adjust fuel/air ratio. Adjust timing. Replace the air cleaner. Inspect and if necessary, replace the distributor cap and rotor. If you replace the distributor cap, replace the spark plug wires. Inspect and if necessary, replace the spark plugs.

You didn't mention how many miles are on your '85, or how long its been since your last tune-up, but, replacing the above mentioned components can't hurt (except maybe your wallet) ;*)