brake booster/s

[alex]

Hey all,

because a good friend is a mechanic for vermeer in comm city, and i'd like to prove him wrong :thumbsup:. (unless he's actually right :mad:)

So in everyone's opinion; as my gromet to the valve and hose to my brake booster is old/erroded(?) it has a vaccum leak in that connection directly from the booster to the tiny valve.

Question: would the engine run lean or rich? because the vaccum is of course after the mass air flow on the manifold, and even after the throttle body.

the mechanic says lean. . . .

[Warrlord]

Lean. Unless the ECU over compensates for fuel delivery but that rarely happens.

[dannan_w]

X2 lean

[Digger]

3x Lean

For computer controlled vehicles, it depends on the system. I watched a Fiero turn the exhaust manifolds glowing red in 2 minutes because of a cracked EGR tube. On the other hand, the Fords I have own have compensated quite well. They usually turn down the idle air bypass valve and use the O2 sensor to correct the A:F imbalance.

[alex]

cool cool. so whats the explanation for lean then? i'm just puzzled, because after the air passes the MAF, it then enters the manifold, and the computer thinks thats the correct mix, however once in the manifold that same air goes to the one-way valve to the booster, but its leaking from that gromet seal connecting the check valve to the booster. so if the manifold is essentially loosing air and the computer thinks its getting more air than receiving, wouldn't there be more fuel than air mix, therefore run rich? lol or am i just messed up in the head???!!! lol. thankx guys for helping me realize what the deal is :thumbsup:

[alex]

oh and Digger you're correct on that with fords, at least mine to a degree. it runs alright for the loss of air, but it idles very low or high at times due to the frequent changing vibrations changing how much air leaks from the seal. but on the highway she does fine, but the giddy-up and go not so much. appreciate the words of wisdom!

[Hypoid]

Take my advice and put some BBQ sauce on that crow that you are eating; mmmmmuch better! :)

You are confused about the leak at the booster. Air is not leaking out, it is leaking in. So, your manifold is sucking down air that is not measured by the computer. That is why MAF systems are so sensitive to vacuum leaks.

There are more variables between manufacturers than I ever bothered to learn, not to mention software changes to existing systems. Pass me that BBQ sauce when you are done with it?

[Glass]

He should be able to show you lean / rich / normal a/f indications by spying on the O2 sensor readings with a scan tool while the engine is running. Hook it up and watch the readings with the leak as is, with the hose totally disconnected and no restriction, and with the leak fixed. Use voltage spec for O2 sensors as the guide, follow the voltage thruout the changes, and see how rich / lean it is at those different stages.

[dannan_w]

If it is/ was a turbo motor then you would be correct.

[alex]

OK! got it, see it seemed that air was leaking out, rather than getting sucked in. but it thats the case then, ya no doubt it'd be lean. :D:thumbsup: thanks guys!