A/F ratio question

[rangerin]

I'm pretty sure my A/F ratio is off. It's an '84 with a carbd' 2.8 I am at work so I can't check vacuum or my plugs right now, but the exhaust has more than normal steam when warming up and the exhaust odor is pretty strong. It doesn't smell like gas, but it stinks real bad and does burn the eyes a bit. I know my head gasket is fine as I recently changed it and when I checked my oil the other day, it wasn't milky. Other than that, the truck runs fine.

Obviously checking plugs and vacuum will help a lot, but can anyone tell if I'm running rich or lean?

 

[RonD]

Burning extra fuel will cause a Greyish "smoke" out the tail pipe.
Burning water/coolant will cause a white "smoke" out the tail pipe.
Burning oil will be black "smoke"

You mentioned "steam" so that would be white "smoke".
And that would be water/coolant.
Check coolant level to be sure.

Because you have a V engine the intake manifold will have coolant circulating thru it, coolant can leak into a cylinder from there, although that is very rare without also having an external coolant leak at the intake manifold.
As you mentioned, a leak in the head's cooling passages is more likely, coolant in the oil can happen but not having coolant in the oil doesn't mean the head is OK.
New head gasket can go out so that doesn't take blown head gasket off the table.

White, sweet smelling "smoke"
Loss of coolant, or over full overflow tank
Super clean spark plug in one cylinder, it gets "steam cleaned"
All point to a cylinder to cooling system leak, i.e. cracked head or blown head gasket

About the head gasket, why did you "recently change it"?
If there was a previous leak there may have been an underlying cause that wasn't fix with only a new gasket.


As for Air/Fuel, Cat converter will get very hot trying to burn extra fuel off if exhaust is rich, you will hear it creaking and popping as the metal expands and shrinks after shutting engine off.
As said you would see grey "smoke" and MPG would be getting bad.
Spark plug tips would be blackish instead of light brown.
And you wouldn't describe exhaust as "steam", no one would, they would say "smoke" in a first description.

 

[adsm08]

The cats make water out of hydrocarbon and carbon monoxide. Water makes steam. The colder it is out the richer it will run (even with a carb) until it warms up. More fuel means more HC and CO.

I don't know how cold it's been there, but this time of year that is usually a byproduct of the weather.

 

[saskbill]

Burning extra fuel will cause a Greyish "smoke" out the tail pipe.
Burning water/coolant will cause a white "smoke" out the tail pipe.
Burning oil will be black "smoke"

You mentioned "steam" so that would be white "smoke".

I may be wrong, but wouldn't it be:

* White to bluish smoke, stings the eyes and wrinkles the nose - oil burner
- above, but just when first starting - valve seals
* White smoke, normal exhaust smell, goes away when outside temp warms up - normal exhaust
*Excessive white smoke, sweet smelling, still lots when engine warm and ambient temp warm - burning coolant
*grey to back smoke, inside of exhaust has carbon buildup, in extreme cases raw fuel odor - running rich

?

 

[kimcrwbr1]

Is the motor running with the computer or has it been sparked? Smack the muffeler with the palm of your hand. If you hear alot of stuff in there the cat is probably shot and needs replaced if your running on the computer. Put your hand behind the tailpipe and have someone press on the gas peddle. As the rpm increases so should the pressure coming out the tailpipe. My 2.8 with the duraspark conversion puts out alot of steam when cold out and I still have the air pump and cat still working. I noticed much better performance with the new cat and muffeler. I bought the parts and my muffeler guy charged me like $40 to install them took about 15 minutes.

 

[kimcrwbr1]

When you had the heads off did you replace the valve guide seals? A common problem is oil dripping down into the cylinders. After the engine is hot and after sitting for a bit if you get a large puff of black smoke out the tailpipe when you start it you need valve guide seals before you replace the cat. The oil will destroy the catalist in the cat.

 

[rangerin]

First off, thanks for the responses!

The motor (other than the A/F ratio) is fine as I rebuilt it over last summer. It doesn't burn coolant (know what that looks like). I took out the compueter a while back and put in a GM HEI in too. The truck also has a new exhaust with cat.

I pulled the plugs and they do say it's running a tad rich. Grabbed the vacuum gauge and got a slightly better tune, but found out a carb gasket is giving me a vacuum leak also. Strange it would be running rich with a vacuum leak. I'll work on the vacuum leak tomorrow, but the exhaust is back to smelling normal.

I do have a question. Would a car running rich steam more out the tailpipe with a cold engine than if it was tuned properly? Perhaps the cat is working more?

 

[kimcrwbr1]

These motors require 10 degrees base timing period. Did you put a non feedback carb on it? Mine runs best with #42 jets and a 1.08 venturi autolite carb.
http://www.ebay.com/itm/FEL-PRO-Car...Parts_Accessories&hash=item23423beb03&vxp=mtr
Lightly surface the base of the carb and put a new gasket between the carb and this spacer to fix vacuum leaks at the base of the carb. The spacer also keeps the carb from getting too hot if mounted directly to the EGR spacer on the manifold. If your still running with the stock carb put the smaller jets in, time it to 10 degrees base timing and then attach the vacuum advance to manifold vacuum. Turn the idle air jets out 3 1/2 turns each preadjustment and adjust the idle air needles for the highest possible vacuum pressure.

 

[RonD]

Goods news about no coolant loss.

Yes, running rich means Cat needs to work harder/hotter which will show up as more "stream" than usual on cold days.

What carb gasket is leaking?
gas engines have two types of vacuum
Ported(or Timed)
or
Manifold

Manifold vacuum is what is found between throttle plate and intake valves, it is what powers the "power " brakes, and what you use with a vacuum gauge to diagnose problems.
If you have a manifold vacuum leak you will usually end up with a lean a/f, simply because in a carb setup the air passing thru the carb regulates the fuel it "sucks in" from the jets.
If there is a manifold vacuum leak then that air enters manifold without pulling in fuel, and it lowers the amount of air that is flowing in thru the carb that is pulling in fuel.
So more air less fuel = lean a/f

Ported vacuum is any air passage that is between throttle plate and air cleaner, on a carb this is anything above the throttle plate.
As you open the throttle plate the manifold vacuum drops and the ported vacuum increases.
Increased air flow thru the carb increases ported vacuum, that is how the jets work(and airplane wings), air flowing past the jets creates a low pressure which "sucks" fuel out of the jets.
If you have a ported vacuum leak on a carb it can cause more fuel to be pulled in depending on where it is on the carb.