My bmw sometimes acts crazy the tachometer goes crazy and the car stops taking gas and eventually shuts down..but it starts back up the problem comes and goes?? is it the o2 sensors??

SOURCE: BMW X5 2000 problem

hi. did you try to start with the orther key, all bimmer the keys has immobilizer ( key security system build in), some time it lost memory by it self.
good luck

SOURCE: bmw x5 is loosing power and shuts down when taking foot off excel

replace fuel pump!!

SOURCE: BMW 328 i 1997: Start up problems / Stuttering / Engine Light

change the pcv valve its under the intake manifold

SOURCE: 2001 BMW 325i problem: Car runs very rough, but no warning lights

Sounds like a fuel problem , have you changed the fuel filter in a while ? could be the knock sensor or the knock sensor module needs to be replaced.

SOURCE: 1997 bmw 328i not starting

Come on give us more information. Think if you were trying to fix your own problem and you had to explain the problem to someone else with exactly no knowledge of what's going on.

1st off....a key with bad electronics and reader will open the door and that's it.

So that being said does the key turn the engine? If so the key, the program and ecu are ok. Say the engine cranks but doesn't start. Fuel pump. unscrew the access plug on the fuel rail and see if any fuel squirts out. NO......don't ever do this when it's hot..........not that yours is because it doesn't run but I had to say that. The millisecond you turn your key over to get it to try to start...the fuel pump comes on and pressurizes the entire fuel system.

Got fuel pressure, the engine turns but still no start= ignition spark plug engine computer problems.