Hope you all can help. I have an '84 with a 300 IL6. I live in Massachusetts, where I failed emmisions for high co levels (3 & 9% at idle & 2500 rpm). It was about 3 times the allowed. Since I had a junk yard intake & exhaust manifold with the O2 sensor, I changed the O2 sensor. The dern computer fails me still. I was told to try to adjust the air / fuel mixture. Ok... how? I have no idea what to do. I know theres an adjustment on the carb, but when will I know when it is not running rich anymore? Is this done at idle?
On a side note, I noticed when I drive highway speeds, my gas gauge moves up a needle width. When at idle, it drops. Any connection?

Thanks in advance
Walter

 

I posted a question a while back dealing with mixture adjustment. I found a procedure to adjust the mixture by reading the dwell (on/off time) of the feedback solenoid on the carb. No one replied so I guess no one knows anything about it. But, in the mean time, I just adjusted the mixture screw for maximum intake manifold vacuum at idle (20") with a vacuum gauge. (I know before I rebuilt my carb the first time, it was 2.25 turns from all the way in.) Hiwever, I had my smog test last week and failed it (gotta love CA) but I had 0% CO and low hydrocarbons emissions so I don't suspect a mixture prob. I failed due to NOX emissions which usually means something is wrong with the EGR sys. I have tested everything I know associated with the EGR and can't figure it out. I know it isn't stuck shut. It is not getting vacuum from the solenoid when it should (as far as I can tell). I put a gage on the line going to the EGR valve and take RPM to 2500 and no vacuum. I have checked the vacuum line from the EGR port on the carb to the solenoid and the line to the EGR from the solenoid to be good. I have checked the wires good between the solenoid and the ECU. I know the computer can open and shut the soleniod if it wants to via the solenoid test using the code reader. I did the key-on/engine running test and got no codes associated with the EGR. I did get a couple "continuous" codes relating to idle RPM and coolant temp but I'm confident they are gone and/or not the cause. I'm stumped. Anyone out there????

On your deal though Walter, if you're pretty sure either you or any previous owners haven't messed with the mixture adjustment, I'd look elsewhere. Actually, I'm not sure what would usually cause HI COs in the first place.

Good Luck.

'84 F150
YFA F/B
SROD
"Ex" => Bone Stock

 

I had a Mail Jeep that failed HI, and lo. An Oil change corrected the LO, and ran out of gas while troubleshooting HI. I put in 10 gallons of real good Texaco and it passed right away.
It turns out I had been buying Gas from a station that didnt sell a lot of gas. It was old gas.

Speed aint all that important, there were Snails on board the Ark, along with the Cheetas!

 

Heres an easy way to adjust your carb. With the truck running at idle warmed up, turn the mixture screw in till the enginge starts running rough then back it out to the engine runs smooth and your mixture is set.

 

Thanks for the advice. I will give that a try

Walter