I have not noticed it while driving (maybe from the vibrations of the road) but when im stitting at a stop light once in awhile my car will make a wierd thud there is no noise but that is the best way to describe it. The only things that i can thing of are that i just replaced the spark plugs and wires monday maybe something went wrong with that (misfire) and also on monday i took a bad speed bump maybe that messed with the muffler? It still drives fine im just worried about what it is. I have tien s tech lowering springs so thae front of my car is a little lower but i have never heard of a speed bump doing that. Sorry if im rambling, and any help would be appreciated.

need more info, where did the thud come from, front/back/left/right? I dont think a missfire would make much noice at all if you even noticed it, maybe a little backfire. was it just bassy (subwoofer like pound) and about how load? and how long did it last?

Its hard to tell where it comes from besides in the engine..i mean i can feel in in the floor boards and it only lasts for a second. I noticed a couple of time when i was in second gear but its hard to tell while i am driving. There is no noise at all.

check the snaps on your shift cables, and make sure they are working properly.

I can shift fine and i notcie it the most while im just sitting there. But i took a bad speed bump last monday and it sounded like it hit underneeth preety hard.

prolly a bad engine mount..........and vibration from the motor. just my guess............