At the advice of someone from the other forum I posted in (Performance, Engines & Troubleshooting > Ford Inline Six, 200, 250, 4.9L / 300), I am linking to my thread in hopes that someone over here is knowledgeable about emissions on my 300.

To make a long story short, I bought an '84 F-150 last week and I live in one of two counties in Idaho that require emissions testing. I have the hard numbers from the test and am looking to see what I can do to bring the numbers down into the passable range.

Before I spend too much money, I am just wanting to know if it is even feasible to get my numbers down from where they tested. The hard numbers are detailed in the other thread.

The other thread is here.

 

get a wideband oxygen sensor gauge
use the wideband to alter the air fuel ratio to correct level to get rid of the exess fuel.

i believe you are running slightly too rich if you are failing on the carbon monoxide emissions test

the other option is to reinstall the smog pump, and use that to get a waiver.



Tell us which carburator you have also..
if you unplug a vacuum line, does your engine rev faster or slower? this is a test to see if you are running too rich

 

do you have a catalytic converter? If so, how old is it?

 

Here's a chart and a couple of tips that may help you diagnose the problem.

First, "rules of thumb":

1) O2 combines with HC to form CO2 and H2O.

2) O2 combines with CO to form CO2.

3) CO is an indicator of air-fuel mixture richness.

4) HC is an indicator of fuel mixture leanness (or richness) and misfires.

5) CO and O2 are equal at the stoichiometric air-fuel ratio.

6) O2 and CO2 are indicators of exhaust system integrity, sample hose and probe integrity, or both.

7) CO2 is an indicator of combustion efficiency that peaks at or near the stoichiometric air-fuel ratios, and decreases with lean or rich air-fuel ratio.

8) Air injection systems dilute the exhaust sample with O2.

9) O2 is essential for proper operation of the catalytic converter. Its concentrations are essentially unchanged by the catalytic converter, providing a "window" through the converter to the engine. O2 levels are higher on vehicles with properly operating air injection systems.

10) If CO goes up, O2 goes down (inversely related)

11) If O2 goes up, CO goes down (inversely related).

 

If you don't have a smog pump or a cat, what else has been taken off. Doesn't your truck have computer control? That's what it's main job is, to trim stuff for emissions. You can tell if your truck has a computer by looking at the distributor. If the dist doesn't have a vacuum advance unit with a vacuum line going to it, it's computer controlled. If there is a bunch of other stuff missing on the engine, I doubt the computer is doing it's job. It would probably pass very easily if it's computer controlled and all that is hooked up and working.