i hav a 2006 mazda 3 w about 80k miles on it. about 6 mos ago a noticed a small problem w it. every time i applied the break, the engine would struggle a little and the inside dash lights & the headlights would pulsate...about a month ago my car would not start or even try 2 turn over (it wouldnt do any thing when i turned the key). i finally got it started a couple days later. i replaced the battery thinkeng tht was the prob...but now every time i apply the break (while driving), the car shuts off completely & i hav 2 restart it. also if i leav it idle 4 a while, the engine will start 2 struggle so im a little lost in regards 2 wheter it might be the alternator, spark plug, ect....can someone giv me some suggestions on wht it is & how 2 fix it. it would be greatly appreciated!

 

i spoke to the dealership & the guy said it might also be a leak in the brake booster valve

 

classic vacuum leak, could be anywhere - the brakes just add more load to the vacuum system, though it could be the booster too. look everywhere on the engine for disconnected / worn / cracked / rodent eaten hoses and wiring first.
if nothing is obvious you should be able to hear where a leak is coming from if you have someone press the brake while you listen under the hood.

 

thanks djs2571...i took my car to a friend and we checked the the coil/spark plugs and they checked out. it seemed tht the car was ideling @ 500 rpm, but if u check under the hood for the recomended throttle its @ a little over 700. there is a very small screw covered w a clear gooey plastic which we think can adjust the amount of throttle being realesed during idle. anyways, when the car engine was warmed from the long drive to my friends house it seemed to do better when i was driving it home.. i used the hand brake to assist my stopping @ red lights & such. i did an experiment while the hand brake was up, it was now idleing @ 700 rpm and the engine sounded fine ( which is weird because when me & my friend were checking it while in park the engine was struggling). but when i pressed the brake the rpm would go down to 500 rpm & the engine would struggle again...does the brakes effect a vacuum leak in this case?

 

There could be a small leak that the engine can compensate for and when you add the load of the brake on the vacuum system it's pushing it too far and it'll run rough / stall.
It could also be that there are no leaks except for in the brake booster, so when you hit the brake it's causing all the problems.

I'm not sure why it would be struggling in park, that's usually a better scenario.

I wouldn't touch that little goo'd over screw to adjust the mixture, though you can probably set it back to where you started.

To test the brake booster, turn the engine off and you should still have at least one good boost left in the brake. Once that vacuum is gone the pedal will be very hard. If there's a leak in the booster you should be able to hear it leaking when you hit the pedal with the engine off.
For a little background, the brake booster is a vacuum operated diaphragm, when you press on the brake pedal it opens a valve to assist you pushing the pedal. There is a check valve that should keep the vacuum in the brake booster after the engine is off, and that should hold well for a long time (haven't tested it but it should hold vacuum for hours). If you wait a few minutes without pressing the pedal there should still be boost, the longer that you can wait with it working well the better the system. If it doesn't have vacuum left after the engine is off for 10 sec, that's where there's a problem - but it could be the check valve, and not the diaphragm leaking.

I'm writing more confusing now, but hopefully that helps.

 

I have a 2004 Mazda 3 2.3L engine the car runs for 20 min and when it get warm and when i put the car into drive and give it gas the car will shut off and i can turn back on the car but it will turn off when i give it gas i need help please

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