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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