Failed CO emissions-high CO and HC

Hey all,

Hate for this to be my first post here but I just failed emissions pretty miserably and need some advice. CO was at 137, limit 40 and HC was at 4.9, limit 4.0. Test was on IM240 treadmill.

Basics about the truck: Bought it at the end of september, it's an 86 K10 350 on 35's not sure what gears, originally had CA emissions. I recently hooked the smog pump back up in anticipation for testing. EGR is long since gone. Has one cat after Y that does not appear to be original but is stamped CARB compliant. Carb is a Carter AFB. Decel valve that connects to charcoal canister appears to be missing also. I'm not sure how well any of the valves/solenoids related to emissions work at the moment. Based on the 30 some year old temp guage, I believe someone put in a colder t-stat since the guage stays right at 175*. I'm assuming replacing this with a 195* would help?

I think the high HC can be fixed with a good tuneup (plugs, wires, cap, coil, rotor, LOF) and maybe a new cat if necessary. I know high CO is caused by excessive fuel. At this point, am I limited to rejetting (which I don't know how to do but could probably learn) or going FI? Or start with a rebuild(again, could learn)? I do get a slight fuel smell when I shut it off which leads me to think it may be in need of a rebuild. I also have a rebuilt, unused Quadrajet that the PO gave me but I would need to get a Quadrajet intake. Am I on the right track or does anyone have any advice they care to share? I would really love to not have to turn around and sell this truck just because I can't get it to pass emissions.

Welcome to the forums first.
I would start with a good tune up first.
It is the easiest thing to do and it will also make it so you know that those simple to change items have already been done.

I just got done with my 1995 Suburban a few months ago.
Turned out we blew the guts of the cat out the tailpipe.
In went a new cat and we passed like champs.
But that was my path, yours may need a carb rebuild and some other type tuning.

PS.
We love pictures here.
It is the common internet currency.
You seek knowledge, we want photos up front in exchange.

Forgive me for I have sinned. Please accept this donation as atonement.

As far as not knowing, jump in and get after it.
YouTube is a bitchin resource that I wish I had as a kid.

My 20 year old son is my ace mechanic now.
Here is is after a carb and intake swap he did after he rebuilt the new to us Holley.
Never did one before and just watched some videos and put his brain to work.


Little bugger has jumped leaps and bounds in front of where I was at his age with mechanicing on stuff.
Now it seems I finance what he wants to do to it.
Truck runs like a scalded dog now.

Yeah I've been turning wrenches for a minute, I've just not had to mess with carbs and emissions since every carbed vehicle I've owned has been exempt and ran good enough so I dont have much experience there. YouTube is definitely gonna be my friend here once again. I'm not worried about tearing it apart I'd just like to not go in totally blind.

By the way that's awesome that he's diving into it! If I ever have kids I hope they'll have the same drive to not buy a car and just leave it be!

Numbers are reversed. CO 4.9% HC PPM 137

CO should be in the 1-1 1/2% or even lower with functioning cat and air pump. With the air pump disabled [pinch the hoses closed] it is likely very rich. Lean it out, bigger metering rods. Do a lead drop idle mix. If possible, check the exhaust tube temp [heat gun] in and out of the cat. Inlet should be at least 50 degrees cooler that outlet after a short drive. If they are the same or outlet cooler cat is suspect.

Don't be concerned with the HC yet it should be lower after those adjustments.

Here's a way to look at it. CO is partially burnt fuel usually a rich condition. HC is unburnt fuel usually caused by everything else, spark, engine condition, ect. However, high CO will cause higher than normal HC.

fast 99 said:

Numbers are reversed. CO 4.9% HC PPM 137

CO should be in the 1-1 1/2% or even lower with functioning cat and air pump. With the air pump disabled [pinch the hoses closed] it is likely very rich. Lean it out, bigger metering rods. Do a lead drop idle mix.

Don't be concerned with the HC yet it should be lower after those adjustments.

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They're not switched, they are all measured I grams per mile not percentages or PPM.

Thanks for showing your paperwork, but still @fast 99 gives good advice. I also think your plan to tune it up is a good idea, don't forget to check the timing.

Air pump and cat should be functional, a functional EGR will REALLY help off idle emissions, but if it's gone and / or the ports in the manifold are clogged it's likely you can get it to pass without it.

SirRobyn0 said:

Thanks for showing your paperwork, but still @fast 99 gives good advice. I also think your plan to tune it up is a good idea, don't forget to check the timing.

Air pump and cat should be functional, a functional EGR will REALLY help off idle emissions, but if it's gone and / or the ports in the manifold are clogged it's likely you can get it to pass without it.

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Yep wasn't trying to disregard his advice, just want to make sure everything was clear. I'll have to see if I can track down an IR temp gun and check the cat.

TurdTaco64 said:

Yep wasn't trying to disregard his advice, just want to make sure everything was clear. I'll have to see if I can track down an IR temp gun and check the cat.

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I didn't necessarily think that you were, I was just going to say something very simpler Brian, an why say it twice.

TurdTaco64 said:

Forgive me for I have sinned. Please accept this donation as atonement.

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SEXY stepper but please for the love of god put GM mirrors on it and JUNK those F150 mirrors it has now!

78C10BigTen said:

SEXY stepper but please for the love of god put GM mirrors on it and JUNK those F150 mirrors it has now!

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He does have dual shocks up front, that should count for something? But it doesn't cover for the sin with the mirrors.

If you like the mirrors, keep 'em.

A good tune up may be all that is necessary, and checking and setting timing. You could probably cheat the carb and lean it out just for the sake of passing emissions. Also, take it for a long drive and get it good and hot before pulling into the test lane, the numbers will be worse the colder the engine is. I'm glad I live somewhere that there is no emissions testing as i'd never pass running 110 octane blended with 93 non ethanol. Lol

Washington used completely different testing standards, PPM HC and percent CO. Sorry for the confusion. I just don't know how high those readings are. The basics still apply, high CO rich, high HC everything else. Do a tune up if needed and lower the CO by leaning the carb out. Many times, high CO will elevate the HC slightly.

Do check that the air pump and cat are working. Combined they are extremely good at emissions reduction.

Harbor Freight has inexpensive heat guns, and they have many other uses.