I have a 90 Accord, and lately it's been doing this weird crap. When I'm at a stop sign or red light, it vibrates A LOT. Like a back massager or sex toy. It's really annoying, and if anyone knows anything Holla. ALSO, when the AC is turned on, it emits a disgusting smell, like dirtiness. Any thoughts???

4 cyl or 6 cyl?

Sounds like you have a blockage in the exhaust. Possibly a vaccum leak. Get under your car and thump on the catilytic converter. If it rattles alot replace it. Blocked exhaust can cause the symptoms you speak of. An easy way to check for vaccum leaks is, go buy a can of throtle body cleaner or brake clean, with engine running spray the stuff all over where the vaccum hoses are (keep a fire extinguisher handy) if the idle speed jumps while spraying you have a leak. Isolate the leak and hunt down the bad hose.

PS, how long has it been since you had your timing belt replaced?

It is a 4 cylinder. And I haven't replaced the belt since I bought the car, which was last August, (I needed it for college). Any thoughts on the smell?

If its smells like a strong musty mold for a short period then goes away, its AC mold. This is caused by trapped moisture in your blending box. Check and clear the drain tube which is supposed to allow the drainage of condensation from your AC system to the underside of the car. If its smells of electrical burning, your AC is going and thats will also contribute to your vibration until the Compressor clutch fails. If not, try a few applications of injector cleaner. This solved the rough idle problem on my CRX-R

If its smells like a strong musty mold for a short period then goes away, its AC mold. This is caused by trapped moisture in your blending box. Check and clear the drain tube which is supposed to allow the drainage of condensation from your AC system to the underside of the car. If its smells of electrical burning, your AC is going and thats will also contribute to your vibration until the Compressor clutch fails. If not, try a few applications of injector cleaner. This solved the rough idle problem on my CRX-R
Uh Huh. I agree with you on that one. How long you been wrenching?

Uh Huh. I agree with you on that one. How long you been wrenching?

Since about 1983.

My problem on my 91 accord was motor mounts.

if it smells like old old water or mold, then its a/c mold, its normal, i suggest when you are about to come home or w/e you are going, turn the a/c off, so the cold air runs out, cold air=moisture=the smell

Mine had a mouse/bird nest in evaperator coil. Took cover off vacuumed cleaned coil MUCH better now. 1993