My car goes lean, pressing the brake pedal not moving

[Jiggalude]

Like the title says. I pump my brakes with the car on, sitting in the driveway, I can peg the Wideband gauge to the red, completely off the charts lean. I disconnected the hose from the intake manifold that runs to the brake booster. I capped the intake manifold nipple and pumped the brakes. Still did the same thing. I don't know how pumping the brakes with the vacuum source of will still cause it to lean out. I really need to get this issue figured out. Please help!

 

[Black3G]

Have you tried spraying all your vacuum lines and intake manifold with carb or brake clean yet?

 

[Jiggalude]

Yes. But that still doesn't answer the question as to why with the vacuum line off the brake booster it would still go lean. I understand if there is a leak that it would make it go lean, but I eliminated the source and it still does it. I'm starting to think it might be electrical or a bad battery. Does that make sense at all?

 

[DSMTyson]

My car goes a little bit leaner when i press on the brakes and stop while it is still in drive.

 

[Jiggalude]

If I hold the pedal down hard it goes lean. I just don't understand why if the vacuum source is off it still goes lean. My battery is pretty weak. If I turn my lights on the car will go a little leaner.

 

[Skippysnax]

I suppose it could just be a strange coincidence that as you blocked off the lines your battery diminished. If the connections or battery are weak enough, anything is possible really. I would say that's most likely not the problem. I would let the car idle and then crank the wheel back and forth. If the power steering causes the car to lean out also then it would be electrical. let me know what you figure out.

 

[Jiggalude]

I suppose it could just be a strange coincidence that as you blocked off the lines your battery diminished. If the connections or battery are weak enough, anything is possible really. I would say that's most likely not the problem. I would let the car idle and then crank the wheel back and forth. If the power steering causes the car to lean out also then it would be electrical. let me know what you figure out.

Thats a great idea! Thanks

 

[Colt4G63 also]

I think there's too much draw on the circuit, and/or you're having a voltage problem when the brake lights or headlights come on.

 

[Jiggalude]

It seems to be that. Like I said I removed the brake booster hose from the Intake manifold and it still went lean. There's no way it's a vacuum leak. I think it's the battery, like I said I've had to jump it 4 or 5 times now.

 

[kchaazz]

This is a normal occurence and every car Ive ever pumped brakes in has been subject to idle changes when you pump the pedal. Notice how your idle climbs higher the more you pump? Its because when you pump the pedal, you force air into the motor from the vacuum booster. When the pedal comes back up, the booster fills with air- it is physically impossible for this air to come from the engine, since there is a check valve incorporated into the booster to manifold hose to prevent boost from entering the booster, therefore, when the pedal comes up, it has to be filling with air from the backside of the booster, probably through another one way check valve of sorts. When you push the pedal, you force this foreign, unmetered air into the intake manifold, which is forcibly pulled into the motor via engine vacuum, which is what causes the pedal to be so easily depressed. Its inconsequential, do not worry

Crap, I didnt catch the other posts about batter voltage issues.....