i have a 91 honda accord lx and i am having a problem with my speedometer and my odometer. the two only work sometimes. for example, i could be driving and it will just start working and the odometer works only when the speedometer and doesnt work when the speedometer doesnt. is there any kind of cable that could cause the problem? also my car idles rough. when stopped at a light or stop sign the rpms sometimes go to about 200 or lower but other times a little higher to about 400 to 800. i got a tune up, spark plugs, wires, etc.... but i am not sure what it can be. any help will be appreciated.