hello,

i need some expert help. i've been trying to figure this out on my own and i'm at a dead end. car is a 2000 LS, manual. bought it 1-2 months ago. all stock, except for some kind of aftermarket clutch (nothing extreme, but obviously not OE).

symptoms:
only when fully in gear, the car bucks wildly when getting on or off the throttle. for instance, i'm cruising along (most noticeable in 2nd in 3rd), let off the gas and BOING BOING BOING and it settles down. then i get on the gas again and BOING BOING BOING. it may sound like i'm exaggerating, but i'm not - it's like i'm headbanging in there. basically there is no way to smoothly transition between 0% throttle and 1% throttle, no matter how gently i try. when it's bouncing around, the revs are not jumping or otherwise significantly affected - it's not like an engine/induction issue. there is no sound associated with this. again, this only happens when staying in gear - no clutch involved. the clutch engages without issue.

what i've done so far:
needless to say, i immediately assumed it was the rear mount. had a look at it, and it was indeed torn on both sides and needed replacement. it was also missing a transmission bolt (not the one on the end of the Y plate, the more central one).

as i began to install a new mount, i realized the reason for the missing bolt is that the "input" for it on the transmission case was broken off - it cannot be put back in. bummer, but i was told it's just one of two bolts, and shouldn't be a problem. i finished installing the mount like normal otherwise, and....nothing. didn't fix a thing. car still boings around like before.

the two side mounts "look" fine. i don't want to replace them for no reason - could they look ok yet still be bad? what the hell else could this be, if not mounts? what would make the exact same feeling of an engine bouncing around on rubber bands, if the mounts are ok? could the missing 2nd bolt somehow still be causing this? i can even see the shift lever bucking in the boot - how could it not be mounts?

any thoughts? advice? what would you guys check next?

 

id say if the whole car is lurching forward and backwards as your giving it throttle, it could be a tps (throttle position sensor) i just had to replace the throttle body on my gfs b16 ef. cuz the car would lurch and bog under full throttle

 

replace those two front torque mounts. they might look fine, but that's not to say that the rubber has stretched and weakened giving you the rubber band efftet