Nissan Technical Advisor 10/5/2010What you mean here is that you're pressing hard the acceleration pedal, but the output speed is not desirable? Usually the causes of this are; the fuel filter is blocked as well as the air filter, the ignition timing is incorrect, uneven or low cylinder compressions, the fuel injectors are blocked, the brakes are binding and a low fuel pump delivery.
Mikhelin 11/2/2010look in transmission sensor...Its in all about Transmission. You mentioned the engine is strong but weak speed, common to blame in drive train. don't keep drive too long..it will explode transmission. i hope you have a lot of money to afford.