BMW: knock sensor, vacuum hoses, bmw 325i

Question
hey whats up?
i have a 1993 bmw 325i manual with 106,000 mi. the car is in excellent shape with one original owner who maintained the car unbelievably. i have been having a problem with the acceleration hesitating. i took it to the shop and they replaced the upper knock sensor and tuned it up (new plugs, filter, ect..). it ran great for about a week and the problem came back. what it does exactly, when accelerating, the car feels as if it were not getting gas. it accererates good till about 2000rpms then, it looses power. if i pump the gas, the power kicks back in, but i have to slightly pump the gas. sometimes it will do this around 4000rpms, i can never tell. sometimes it will not do it at all. this is in every gear, mainly second/third.
the check engine light is on and i tried to do the self diagnostic, but it didn't work for me.

i know how the car is supposed to run and it def. has a power loss. could it be the lower knock sensor?and if so how hard would that be to change?

also, where can i check transmission fluid?

thank you very much!
kenneth  

Answer
Let me answer the transmission fluid part first. I am assuming this is an automatic. You really need to take it to the dealer for that. You have to hook it up to a diagnostic machine that can tell the temp. of the transmission and when it gets between 30 to 50 degrees celcius the and only then can you check it, and it is a very small span of time there. More than likely they will want you to leave it over night. Now, where to check it is depending on what transmission you have. They have a drain plug above the pan that you open on some. Some other transmissions have one towards the rear of the pan in a well. It is best to take it to the dealer. On your other issue, does the check engine light come on at all? There are soooo many things that can cause this concern. I would start by looking at vacuum hoses. After these vehicles get some miles on them they tend to get oil soaked and melt apart. A few other things that can cause this issue are, mass air flow meter, throttle posistion switch, coked up throttle body, and many other things. I have even seen the wire that excites the starter loose and cause this issue. Sorry I can't give you a direct on what is causing this. Let me know what you find or if you need some more info.