Hey everyone,
I have an '81 Bronco with the 300. This was it's first emissions test while in my ownership (about 4 years) since I just moved to an area that requires one. I knew it would never pass, so I have been working on tuning it, double checking to be sure vacuum lines were routed correctly, and I also put a new exhaust on from the engine all the way to the tailpipe. It purrs like a kitten but it still failed. It also has a slight hesitation when accelerating.

Here's the test results from today:

2500 RPM Test:


CO% Require: 1.20 Me: 1.75 Fail
HC(PPM) Require: 220 Me: 125 PASS
Dilution CO+CO2(%) Require: 6.00 Me: 15.55

Idle test:

CO% Require: 1.20 Me: 10.77 Fail
HC(PPM) Require: 220 Me: 1241 Fail
Dilution CO+CO2(%) Require: 6.00 Me: 18.67




Any ideas? It's the first time I've ever emission tested anything so I'm not sure where things come from. Thanks for the help.

 

when you put in the new exhaust, did that include a new catalytic converter as well?

 

Did they give you a paper for idiots like us to "figure" out what of a zillion things could be wrong as they do here in Delaware?

Your test sounds just like here.

I have "heard" that if you put 4 or 5 bottles of a certain gas line anti-freeze in a YELLOW bottle that rhymes with HEAT and a 1/4 of less tank of gas will pass you.

Stuff is pure Methanol and Methanol does not put out CO or HC'S?

This is purely ed-u-cational, and pure hear say, uknowhatimean?

 

Yeah, the cat is brand new as of last month.

And I've heard of the methanol trick. I might give it a shot if all else fails, but I would rather my truck be running right. I see emissions as a doctors bill, if it fails, something under the hood is unhealthy (if all the emissions stuff is hooked up anyway).

And yeah, just a bunch of numbers. Although they were kind enough to provide a list of local mechanics.... So kind.

 

Did they not say what they think it could be?

I wonder if you install a temporary second cat if that would help pass you. Then you could just take it off untill next year?

 

iT COULD BE ALMOST ANYTHING WITH A 27 YEAR OLD TRUCK. LEAKY EGR'S ARE COMMON AS ARE LOOSE HOLD DOWN CARB BOLTS. Sorry about the yelling.

 

First, I've got to give you applause for driving a big Bronco! I almost never see them anymore.

Let's see...puking rich at idle (maybe- from your smog #s), slight stumble on acceleration, and purrs like a kitten. Is this acceleration from a stop, accelerating while driving, or just general acceleration? Does it smell super-rich at idle? Did you put on an OEM-style converter, or aftermarket? Give us some more symptoms, and we'll try to help you out.

In addition to making sure your EGR is working, may I recommend the three "R"s of troubleshooting the old YFA carburetor on your truck: Rebuild, Replace or Retrofit. I hear replacement remanufactured carbs are often junk. If you're handy, you may be able to rebuild it, but that could turn into real work if the throttle bushings are worn, etc.. I'd recommend you purchase a 1BBL to 2BBL adapter and bolt on a Motorcraft 2100 2BBL, with the 1.08" venturis. This is a very common carburetor, and I've only ever heard good things about it. Easy to install, easy to tune, and runs like a dream.

 

Thanks for all the help everyone.

The acceleration thing is pretty much when I start off in low RPMs from any given gear. It doesn't miss or anything, it just dogs for a moment and then picks up (almost could be described as feeling like turbo lag.)

The carburetor has been rebuilt, and the cat is by Walker. I think it's one of those 3-ways. The oil was also changed a few weekends ago.

How do I make sure my EGR is working? I know all the vacuum lines are hooked up.

Here's some things worth mentioning:

If it has anything to do with oil, it is low on oil because it keeps leaking. More oil is on the shopping list since it's again below the add line.

I converted the exhaust manifolds to the EFI dual out. I haven't put the carb heater on yet.

The EGR is all hooked up except for the EGR pipe that comes out of the manifolds and back into the carb spacer. It's sealed off since the exhaust shops told me that with today's better fuel and cat converters, the difference a little bit of recycled exhaust was going to make during emissions was pretty insignificant.


So from what I can tell, the emissions stuff is working "pretty" well since it almost passed during acceleration. It just seems that something isn't tuned right during idle. Especially since the HC is the only one that passed at high rpm, but failed miserably at idle.

 

New EGR with the exhaust tube hooked up and get some heat to the intake.

 

The EGR provides a little exhaust up to the combustion chambers for a more complete burn.

 

Actually, the EGR cools the combustion chambers by putting in inert gas. It helps with pinging, and the formation of NOx.
You need to tune it to run at these altitudes, that's why it's rich. All my vehicles had to be adjusted, my wife's Jeep was way rich.
I just moved here from Bremerton, WA a couple months back. It takes some getting used to the reduced power, but you can crank your timing up and still run a crappy gas like the 85 octane they have here.

 

Nice setup. I'm jealous of your truck.

I second what Harte3 says. Hook up your carb heat. That'll fix the off-idle bog. What's happening is at high vacuums, the vacuum alone is keeping your fuel well vaporized, but at low vacuum, with a cool/cold intake, your atomization is terrible and inconsistent.

A non-functioning EGR will give you a lean condition (ping when it's broken). However, your carb is smog-calibrated, and will expect reduced oxygen at cruise (EGR), so if you've adjusted the mixture to get good-running at cruise, you'll be rich at idle.

Fix your EGR, get some carb heat, then start tuning. And of course, adjust for altitude. However, since it isn't rich all the time, my gut tells me it's probably not altitude that's your problem.

 

Hey Ford_Six, Jerome's actually a bit higher than Boise. I think you're at around 3800ft and Boise is around 2400, so it doesn't effect it quite as much. (Sure notice it when I drive to visit my family in Twin Falls though, they're higher than you.) And yeah, I can imagine you'd have quite a reduction in power coming from sea level. =P

I'll definitely be getting over to plumbing store so I can get some heat to the carburetor. Since the heat riser's been removed with the addition of the EFI manifolds, I made up a plate to run coolant over to it. Just haven't hooked it up yet.

Also, do you think it would cure my problem if I hooked up the EGR tube? I originally planned on it, but it is quite a bit of work trying to fab up that complex of a pipe from scratch since the EGR tube on the EFI manifolds ran in a completely different direction than the one on the carb models.

Seems like from everyone's been saying (here and elsewhere), is that I just need some extra heat in my engine.

And thanks for the compliments, BigBlue88. I love the Bronco, especially with a 300.


Also, they don't test for NOx here, and I'm except from O2.

 

What does sea level have to do with a vehicles power?

 

A lot.
Higher concentrations of oxygen in the air. If you ever go backpacking, the air is so thin at 10,000 ft that if you try running, you will be so out of breath within moments that you won't know what hit you.

Same goes for a car. The higher the elevation, the less oxygen concentration due to less air density, and lower bang for the buck.