We are baffled, so hopefully someone can help. 91 Accord. Has a horrible shimmy/vibration in the front end SOMETIMES. It can be so bad you can barely grip the steering wheel and it feels like the car is coming apart and then it can drive smooth as silk sometimes. No rhyme or reason to when it is there and when it isn't. We've checked brakes, rotors, bushings, bearings, springs, struts and just recently replaced tie rod ends. It is definitely front end. The only thing left we can think of is maybe a belt in a tire, but can't believe that would come and go, nor cause this bad of a vibration.
Any ideas?

 

rotate your tires front to back...

i had a bubble in the tread or a shifted belt before, but vibration was constant so it may not help to find your problem

how's the condition of the cv halfshafts?

 

^^^ this would be my vote.

if you rule out the other intermittents (brakes, alignment, worn suspension components, engine mounts...) this is the major one left. i've recently had the same issue. after a lot of testing and checking i had ruled out everything other than the axles. for testing/learning purposes i replaced the side that seemed the worst; vibration reduced by about half! i still need to get the other on... but i would recommend replacing both at the same time.

how many miles are on the current CV joints?

also out of curiosity, is it a manual or auto trans.?

 

So speed has no effect at all on the condition? It is purely random?

I'd agree with those who have posted above me if you have not checked those parts. Otherwise you could check and make sure your wheels are not out of round or a tire isn't bad (like ricebike suggested). Just had to replace one myself and now the ride is smooth as silk...

 

Did you check car behaviour under power versus not powered? An easy test: as soon as the vibration occurs, lift your foot off the throttle and put the shift lever into N. If the vibration does not stop then you can rule out the powertrain as problem cause. (you can safely change the shift lever back to D position while the car is rolling).

 

Is the road really bumpy?