Not another emissions thread! Ugh. (1 Viewer)

Chad717

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So I hate to do it but I thought I would throw it up here because the Mud knowledge base is so deep. I have read almost every emissions thread I can find, and I am determined to get this figured out. I'll give as much detail as I can. First of all the emissions readouts:
HC: Pass
NOx: Pass
CO: 143 GPM, limit is 45 (rich right?)

I live in Colorado and our town is at roughly 6500 ft elevation.
Brand new rebuilt 2f, less than 100 miles on it.
Rebuilt carb (well i rebuilt it 2 years ago when I first started attacking this problem, it sat for 2 years while I was getting the engine rebuilt)
Brand new Cat.
Rebuilt smog pump by B-Z rebuilders in California.
All brand new vacuum hoses that are presumably hooked up right. (i'm in the midst of policing my work right now)
ABV works according to tests in FSM. Also inlet hose to smog pump has suction, and the bypass hose is not blowing any air out back into the air filter.
Brand new plugs, distributor cap and wires.
Timing set to 10* with the vacuum hoses unplugged. HAC works to bring the timing up to 16* when plugged in.
Idle mixture screw set using highest Vacuum with idle speed screw set to about 450-500 rpm. About 18 inches.
No vacuum leaks, my vacuum gauge shows 18 inches steady at an idle of 650-700 rpm. This is at 6500 ft elevation.
Choke shows fully open when hot.
Brand new air filter.
Oil has only the mileage on it since rebuild.
New rear brakes might be dragging a bit, just installed new shoes and drums.
Stock size jets.
Fuel in Carb is a little bit higher than the middle of the sight glass during idle.
H55f, so a five speed for the emissions test.

All I've found so far is that the vacuum hoses to the HAC, the ones that go to the Upper Left and Upper right were reversed. I know that this could cause a rich condition, but i'm almost 3 times over the limit, so I'm not sure this will solve it. The CO on the speed graph is high at speed not at idle, so i'm also not sure changing the idle mixture screw to lean it out some more will help.

I'm about to take it for the 3rd test after I switch the HAC vacuum hoses. If it fails then I guess I'll throw some E85 in it? Thanks for all the help on here!

Chad
 
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Chad717

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Do other people in Colorado go down a Jet size? It had smaller jets on it when I got it and it ran terrible. I thought that the HAC etc. would compensate enough for the altitude....
 

OSS

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Wow so everything seems top notch with the engine- all new rebuilt stuff - yet it's running rich. A lot of the typical run-down-the-list emissions checks for high CO you've already addressed, so it seems that -maybe- the carb needs those hi-altitude jets to pass smog. The high altitude jets just have a smaller opening to allow less fuel, so they may be the silver bullet.
It may be a pain to swap them back in, but I'd do it for the test (and swap em back out afterwards if you don't like how the engine runs).
Yeah - definitely triple check your vaccum line hook up to the HAC and carb. It will be crucial at your elevation.
Also make sure engine & CAT are all up to temp before taking it to test. Drive it for 20 minutes at least & don't turn it off while waiting to be tested. Needs to stay hot. Of course air cleaner/filter should be new before test.
 

Chad717

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I just feel like I should be able to pass, I must be missing something. Anybody else in the Denver area have a 60 that passes regularly?
 
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I had the same problem when I smogged mine last year (high CO at 2500 RPM, passed at idle). Took it to the smog shop and they kept it for the day. They said they had to spend a lot of time getting my Catalytic converter up to temp and the CO came down and it passed. They recommended replacing the cat.


I am due for smog again in 2 months. I will say that last time I smogged I had a bad thermostat that wasn’t allowing me to get up to operating temperature. Not sure if that was a contributing factor or not.
 
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Test your vsv’s... I chased a failing emissions problem for more months than I care to remember. Put hundreds into fixing things that didn’t matter. In the end it was a bad vsv. My work around was to plug one of the vacuum lines to keep the abv open and dump clean air into the exhaust rather than cycle it through the air intake. After about 8 failed tests the guy looked at me and said “I don’t know how you did it, but your truck is running cleaner than a Prius. Congratulations.”

I’m in boulder by the way.
 

Chad717

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What are the O2 numbers?

here you go @Spike Strip. Can you tell by the O2 how much air the smog pump is moving?

D0196F78-2277-49C5-9E57-4A46FCCBFE1A.jpeg
 

Chad717

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Test your vsv’s... I chased a failing emissions problem for more months than I care to remember. Put hundreds into fixing things that didn’t matter. In the end it was a bad vsv. My work around was to plug one of the vacuum lines to keep the abv open and dump clean air into the exhaust rather than cycle it through the air intake. After about 8 failed tests the guy looked at me and said “I don’t know how you did it, but your truck is running cleaner than a Prius. Congratulations.”

I’m in boulder by the way.
Definitely gonna try this as well, right now all my FSM emissions tests are passing, but I’m gonna go through it again.
 
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How old is your CAT? I needed to get a new one (among lots of other things) mine was destroyed from running rich so long.

I also had a vacuum line reversed at the smog shop. It threw my numbers way off.

I also had a miss in the engine. This is what caused me to do a compression check which told me I needed a new head gasket and all new lifters.

Also, shouldn’t your timing be at 7?

Man... this was two years of this same biz for me. I feel for you but it sounds like you’re really close.
 

Chad717

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@joebattle1 the CAT is brand new. I have the timing advanced a little bit more because I am at 6500 feet elevation, although I am looking for input on whether or not the 7* would be better solely for the emissions test. I was under the impression that at my altitude I can advance it a little more to get better combustion. Thoughts anyone?
 

Seth S

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A side question as I don’t live in a smog state: Does a 1980’s vehicle have to meet 1980’s emission results or modern requirements?
 

OSS

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One of the oldest tricks in the book to try to get an engine to pass is to retard the timing. That's specifically why the timing is technically supposed to be checked during a test (to identify cheaters). Definitely knock it back down to 7°. Advancing it does you no favors at the smog shop.
Since your NOx is really low, just add some alcohol to the gas tank & call it a day (about 10%). It'll pass.
 

Chad717

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I set the timing back to 7* and fixed the reversed HAC vacuum lines. Took it in and it actually got worse.
There isn’t any E85 gas in my town or else I would have tried that, I don’t have plates on it currently so I didn’t want to drive to far. Gonna run as many of the FSM emissions systems tests that I can, again.

A1EE048F-8CFE-44AB-8883-77C26245CFE2.jpeg
 
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Definitely gonna try this as well, right now all my FSM emissions tests are passing, but I’m gonna go through it again.
Oh the amount of times I tested things and they passed... I had to actually put a multimeter on the vsv to know for sure it was non functional. I wish I had done that in the first place. I just assumed the smog systems would fail if the vsv was bad. The valve is suppose to open at a certain rpm to allow clean air and exhaust to be recirculated. Well, when I hit that rmp on the dyno my numbers spiked 3-5 times. I couldn’t figure out why. So I replaced EVERYTHING that was availible. OSS posted something about plugging the vac line to cheat the egr and dump clean air out the exhaust. Actually I think Jim was the one who started that idea. Works very well!
 

Chad717

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Oh the amount of times I tested things and they passed... I had to actually put a multimeter on the vsv to know for sure it was non functional. I wish I had done that in the first place. I just assumed the smog systems would fail if the vsv was bad. The valve is suppose to open at a certain rpm to allow clean air and exhaust to be recirculated. Well, when I hit that rmp on the dyno my numbers spiked 3-5 times. I couldn’t figure out why. So I replaced EVERYTHING that was availible. OSS posted something about plugging the vac line to cheat the egr and dump clean air out the exhaust. Actually I think Jim was the one who started that idea. Works very well!

I'm definitely interested in this, and if anyone knows which line to plug i'd love to try it.
 
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I'm definitely interested in this, and if anyone knows which line to plug i'd love to try it.
I forget or I’d tell ya. I just took a piece of a twig and shoved it into the line far enough that I could connect it back to the ABV and the shop wouldn’t see it. It’s that simple. Maybe two lines?
 

Chad717

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I forget or I’d tell ya. I just took a piece of a twig and shoved it into the line far enough that I could connect it back to the ABV and the shop wouldn’t see it. It’s that simple. Maybe two lines?

Also I have a multimeter but i'm not to good with electrical stuff, how do you test a VTV with it?
 

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