Bump when taking off

I have an 88 Thunderbird 3.8L. When accelerating off the line it feels as if I am running over a small pipe on the road. That's the only way I can explain it. It's easy to duplicate and only happens when you stomp on it, at least half throttle off the line. I don't see anything wrong visually. I took the drive shaft loose the other day and the U-joints felt OK, one was a little stiffer than the other on the front end, but none were bad. I can only visually inspect the motor mounts, but they look OK and the engine does not rock in the engine bay when revved. I noticed the other day that a small amount of smoke from between the firewall and the engine will be visible on rare occasions. The engine does not leak or have any other problems. When driving normally everything seems to work well, no sounds, bumps or other signs of misbehaving.

Any ideas?

did it always do that or is that something that just began to happen recently? My car kinda did the same thing. I was thinking that maybe the dude at the parts store gave me the wrong size front rotors, because they have a little bit of play in them, and the mental image I got from taking off and getting the feeling you talk about, was that there was play in the lug bolts and rotor holes, which caused it. I never really tried to figure it out though, so I dont know. Have you replaced your rotors recently?

About the smoke you saw, next time you see it, look under the car and see if the smoke is coming off the resonator, or any part of the exhaust. There may be a slight leak that splatters onto your pipes. My car would leak tranny fluid under high pressure, and it splattered on my resonator and burned off, and the smoke came from between the engine and firewall like you said.


Rick

did it always do that or is that something that just began to happen recently?
Rick

It has been doing it for some time, before and after brake jobs, which I do. It shows up only under hard starts, braking is fine,


About the smoke you saw, next time you see it, look under the car and see if the smoke is coming off the resonator, or any part of the exhaust.
Rick

The engine and trans do not show signs of leaking, it appears like it may ge coming from the bell housing. Something inside maybe?

Loose or broken tranny mount?

i like the tranny mount idea first.but i do no the stock motor mounts stink i broke 2 sets w/ my hard driving on only a stock everything 87' T-Bird.another way to check them instead of just reving the car is with the hood open so you can look at the motor from the drivers seat (or get a friend to look) at each mount. power break the car in both forward and reverse giving it enough gas but not to much remember keep this safe so make sure your foot dont come off the breaks the idea is to see the motor move alittle bit not alot if its broke it will move alot and slam back down making a bang. now if they are broke thers a good chance they made your tranny mount bad causing that bump felling your felling.