I test drove a 1994 300zx convertible yesterday and it was very sluggish. the engine made a grinding/pinging noise and the pull off was slow. the owner said the car was sitting in his garage for a couple of years. i stepped on all the way down on the gas pedal and the take off was slow and the did not go more than maybe 40mph top speed. is this the effect of the car sitting for so long or the engine or transmission or both has a problem?