Toyota Repair: 1988 Toyota Tercel engine idle stalling, rich fuel mixture, intake manifold gasket

Question
Hello, I have a friend with a 1988 Toypta Tercel,. The problem we are having is the engine will not run without constant play of the accelorater pedal. I seems to run weekly as we do this, ie lacking power. Seems to me it is a rich fuel mixture caused by a sensor or a vacuum. He has replaced the carburater twice to no avail. I have also been inclined to check the o2 sensor, but don't believe that is the main problem, because engine simply wont run and I am not sure what voltage a good sensor puts out on this make of car. Any advice ?

Answer
The O2 sensor won't cause this problem, there is an intake leak somewhere either at the intake manifold gasket where it connects to the cylinder head or at the carburetor base, there could also be a large vacuum hose that is not connected.
Try spraying some carb cleaner around the intake manifold area and see if the rpm changes and goes up, if so that's  where the leak is.