Why altima will not accelerate. HELP!!!

-scan for trouble codes -check air filter --map sensor [clean if dirty ] vacuum leak --cat converter--fuel filter

if engine is revving and in drive and does'nt move must be a gearbox /drive train problem,is it a manual gearbox ? if it is then i'd say get the clutch changed as pressure plate failure would cause this type of sypmptom let me know how you get on

run the fault codes
most likely a problem accelerator position sensor , throttle body motor sensor or wiring fault

replace your accelerator cable.

did you have a cam / crank relearn performed? also does the car idle over 1000 rpms? is the service engine soon light on?

these are notorious for this problem-a leaking intake gasket at #4-it can be verified by using a can of carb cleaner. Spray around #4 intake port, if the idle changes you have the same issue. Do NOT clean the throttle body on these cars, it is so sensitive that a 25 RPM change will set another code that you'll never get rid of unless you replace the entire throttle body. I work on my neighbor's Altima, there are no shortage of quirks with these cars. Here is a link specific to your issue, with owners who want a class action against Nissan:

http://www.obdii.com/ubb/Forum1/HTML/002735.html

4- 600 rpms idle maybe

when was the last tune up done ?

It sounds like you may have a vacuum leak. Your car should normally idle at about 700-750 RPM. You said that yours was at about 1000-1500, that is waaay to high. If you have a leak somewhere in the system the car will draw in extra air and it will want to idle much higher and will also be very erratic and hard to drive.

the first then i would check for is a vacuum leak, does the car make a hissing noise under the hood?