Hello. I have a 91 accord ex sedan AT with 122,000. I've had this problem with the drivetrain since I've owned the car. Transmission "wobbles" or shakes under light acceleration at speeds between 35 and 50. The shaking goes away if I let off or give it more gas. Since I've had the car I've done a lot of maintenance. Exhaust(factory), EGR cleaned, basic tune up, fuel filter, throttle body cleaned, 02 sensor, T-belt, thermostat, valve adjustment, all the seals you could possibly replace while doing a T-belt job, front motor mount, both axles, tranny fluid changed(it is still red not burnt)wasn't burnt before changed either, and front brake pads. The engine performs great 27 mpg avg. and runs strong. After all this maintenance the transmission still has this annoying shake. Clicking on the sport button makes it go away at the lower speeds but is still a strong shake between 40-50.
My only guesses left are: the rear motor mount(over $300), faulty lock up solenoids, something internal(warped torque converter, can this even happen?), or it's just old and worn. Another transmission issue that is not really related to this is the down shift from 3rd or 4th to 2nd is kind of weak. For example, when slowing down from 40 to 15 then accellerating again, say to make a turn onto another street, when accelerating again the engine will surge up to about 2500 or 3000 then drop down into 2nd gear. Any thoughts or suggestions would be greatly appreciated.

 

Just for giggles, disconnect the vacuum hose to the EGR and plug it and try that on some test drives. Open the hood and look between the hood and the under windshield area and watch the engine. Hold the brake with one foot hard, put it in R and give it some gas, let off the gas, put it in drive and give it some gas, back and forth, this is called brake torqueing, see if the engine is moving too much, I know you need a good car to see what too much motion is, this is testing the engine mounts and tranny mount. I assume when you start up cold and drop it in gear that there is no clunk like the engine is trying to twist itself out from under the hood.

EDIT
I wasnt done yet, the next thing may be a lockup problem, lets get one of the other guys try to explain that one or how to turn off the lock up if possible. If you race it through say 70 MPH do you still get this shudder.

 

The shuddering is not felt from 60 mph on up. Will disconnecting the EGR test for a potential vacuum leak?

 

Not a vacuum leak, an EGR malfunction or clogged ports again. Please try.

 

Have you replaced the tranny mounts or just the engine? also, there is a vacuum port on one of the engine mounts that if not hooked up can cause problems .... symptoms don't really fit, but it's worth looking at.

 

I've only replaced the front dogbone(it was obviously torn). My mechanic showed me the others and they all looked fine. Didn't really know what to look for on the rear one(w/ vacuum), all connections to it were good though. I've seen a couple posts that talk about cleaning the lockup and shift solenoids. Could this be the cause and has there ever been instructions on how to clean those guys?

 

Does the car still shake when it is in neutral? Are the tires properly balanced?

 

A CV joint could have a wobble issue at certain drive speed. You could put the front wheels up (jack stands) and very carefully inspect for wobble. This would be a good way to get to the source of your vibration.

good luck

 

The car does not shake in neutral, D or Rwhen not movingand the tires are all good. The shake is only in the 35 to 50 mph range. The shake is there when there is no decrease or increase in throttle.The shakedecreases and goes away if you give more throttle or take away throttle. When in "S" mode it only has the shakes between 45 to 50 give or take.For example, If I'm driving along at a constant 35mph and the shaking is occuring, I click on the sport button and the shake goes away imediatley. The engine itself is in very good running condition, no misfires,no hesitation,good gas mileage, and is responsive.

 

I tightened the cable that goes from the throttle body to the transmission. This made the transmission shift much more crisp. It doesn't make that sloppy downshift going from 4th to 2nd anymore either. It did make the shake go away by about 80%. It is still there but no where near as severe. I know that the cable is there to tell the transmission what the throttle position is for shifting purposes but I'm not sure how it is affecting my shake issue. Any ideas on what's going on with this thing?