doomtoo

How many problems could cause the engine to change(runs like injectors blown one time, runs just like crap another, so on, about everytime I start up the car? I got home, the exhaust is comming out in deisel bursts, the engine is shaking like mad, when I rev it, you can really feel/hear the dot-dot-dot of the engine, and the whole car is rattling (my cd case in the door case is also vibrating against the side).
I drove it down to the mechanic, 1/2 way there, it starts running like it has for the last few months, crappy and hard to accelerate, but not so bad that it accelerates on the ticks(and I could only it took about a minuter to get the car up to 40).
WTF? Something doesn't seem to be loose, par-say, because it doesn't happen over bumps, what in the world could be "loose", but not physically loose?
ARG!
I brought it by the mechanic, he won't have time untill tommorrow morning, but I have school. They will run some diagnostics on it, it'll cost $80, he syas 9x out of ten they can figure it out within an hour. After that, it gets expensive :S