exaust/vibration problems

[alb_accord]

i just finished doing a head gasket job on the car. and i put a new intake manifold gasket etc. now when i took of the head i took it off with the exaust manifold. i took disconected the exaust manifold where the four pipes become two. and i didn't replace the two O ring gaskets.
now after installing it and driveing it i get this vibration at the gas pedale when its 2500 rpms. and i hear a noise like the mufler is bad. where does this comes from. does this come from the O rings or did i had to take to change the exaust manifold gasket too????
the reason i ask is because when i did this job 2 years ago and i installed the two O rings the car still did the same noise.

so anyone did this kind of job and had the same problem???? how did u fix it????

[SkiLLz]

I had something very similar last summer, where at a certain low RPM it would make this horrible resonating noise and it turned out to be related to the cat. Replacing the cat got rid of the noise.

[NoSloCB7]

It sounds like your downpipe is rubbing on something. Its hard to diagnose the problem with hearing it. Does it sound like an exhaust leak, or is it just vibration? As for the gaskets needing replacing....Yeah you should have replaced the gaskets.

[alb_accord]

it sounds like a loud muffler on the car. and i a couple years ago i did change those two O ring gaskets and the noise didn't go away. as for the exaust manifold gasket on the head,,,, i didn't replace that because i didn't take it off.

[darkslide_77]

def sounds like exhaust rubbing on something.....prolly something you did when you put exh manny back on....a heat shield or something??

[alb_accord]

i didn't take off the exaust manifold. i just took it off between where the 4 becomes two. i tryed tighting the 3 bolts there but that didn't help....

anyone have an idea of whats up with this????

[darkslide_77]

not sure....sounds like you have an ex.......or the ehx mani from one....im not that familiar with those, but is there the little bracket that attaches to the block on that one like the dx/lx 4-1?? that would cause a vibration like you mentioned.....

edit: it is between #1 and #2 cyl i think...ill have to go get my old exh many and look