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From: Ph on 23 Mar 2007 08:12
pretty(a)please.org wrote:
> My 1985 corolla with 4A-c engine, federal emissions, Rear wheel drive, 2
>
> barrel carburetor is running very rich, even at idle. This car used to run
>
> lean, and getting to much fuel to the engine is a very recent problem.
> The fuel level is right in the middle of the float bowl sight glass, so I
>
> don't think it is the float or needle valve.
> I recently did run Sea Foam fuel treatment in the tank for the first time
>
> (in the concentration recommended on the can), I don't know if that has
>
> anything to do with this problem.
> The choke is operating properly.
> The AAP functions and there is no fuel in its vacuum line.
>
> The car is driveable if I disconnect the 3/8" vacuum hose that goes up the
>
> the HIC that is bolted onto the air cleaner, and I screwed in the pilot
>
> mixture screw all the way. In other words, I introduced a MASSIVE vacuum
>
> leak just to compensate for this rich condition, so it is getting way too
>
> much fuel. The car drove reasonably well like this, even at 65mph. I only
>
> drove it about 40 miles since this problem developed,it seems to be running
>
> rich at all engine conditions.
>
> The manual says when it's running rich it could be the "power valve" which
>
> is some spring loaded carburetor part. What does the "power valve" do, and
>
> could it cause it to run rich even at idle?
>
> What else could cause it to run rich, even at idle?
>
> Ladies and gentlemen, thanks in advance for the suggestions!
> -Mark Lum
>
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When you say the choke is operating fine, does that mean it starts and
runs well until operating temperature is reached and then you notice a
rich condition? Check the choke pull off. It may have a bad diaphragm
and will not operate. Check the vacuum supply to it, it could be a
temperature / vacuum control as well for that supply. If you look in the
top of the carburetor at operating temperature does it look like the
choke plate is still restricting air flow? Can you move the choke plate
manually to remedy the problem? The power valve systems I am familiar
with are a method of introducing additional fuel so when you stomp on
the accelerator the engine doesn't stall from lack of fuel.
From: Ph on 25 Mar 2007 05:10
Mark Lum wrote:
> The choke is pulling off mechanically, and the vacuum operated pull off
> device holds it wide open, so that isn't the problem. I agree, that
> that's definitely the first thing to check, though.
>
> I don't understand enough about how the carb works to know what would
> cause it to be running very rich, even at idle. Any other ideas?
> Thanks for the input!
> -Mark Lum
The only thing that comes to mind is maybe the needle and seat valve is
not sealing and flooding the engine. Maybe you have a gasket failure
between either the air horn and throttle body, or the throttle body and
the base.
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