92 Honda Accord with an F22a4, with a6 cam, all stock aside from an intake. It was burning a bit of oil when I first picked it up, and threw this "Piston ring sealer" stuff in there just so it would stop burning(i plan on doing an entire rebuild/building it up for turbo). I noticed that the brakes sometimes had "power" other times it did not, so narrowed it down to the brake booster after replacing the check valve; the hissing it gives off after I turn off the car should have given it away from the get-go. I have another, second hand, brake booster sitting in the trunk of the car, just been too lazy to put it in unless 100% absolutely needed.

So the question is, would the fact that there is that large of a vacuum leak caused be the failing brake booster, "trick" the MAP sensor into adding more fuel, or more or less, it notices that there is all the Air Pressure within the intake manifold but adds the fuel accordingly, but with the vacuum leak the A/F ratio is off since some of that air pressure is escaping?

 

Air would be sucking in from the brake booster. Not leaking out.

So my first thought is it won't make it run rich. But it will bring un-filtered air into the intake.

 

Vacuum leak should cause the ECM to detect a lean condition from O2 sensor and increase Long Term Fuel Trim (LTFT) to compensate. If enough LTFT is added a code (probably 43) will be set. You can't monitor LTFT on obd1 ECM's to my knowledge.

good luck

 

I agree with TexasHonda, a brake booster leak will cause a lean (or very lean depending upon the size of the leak) condition. This isn't something you want to drag out, if the leak is sizeable enough the air to fuel mixture could be nearing stoichiometric, and if it is, burned valves and/or destructive detonation are a matter of when not if.

Long story short, my recommendation would be to change the brake booster as soon as possible.