dansaleen_04

94 accord 4dr ex. My boy's car is shaking like hell I took it for a test drive and once you reach 30mph it shakes like hell. checked the tie rods, shafts, sway bar, and even had the car aligned and balanced and it still shakes crazy side to side but rough. the steering wheel doesnt shake just the car itself. I just noticed the front motor mount bushing is torn completely so the bolt is just hanging there really. Im not sure if the front motor mount being busted would cause the car to shake to the sides like that, I figured it would happened with the side mounts instead. And it only happens when you are on the gas, the moment you let off the gas pedal it stops shaking. If you leave it idleing and hit the gas you dont feel it so I am wondering if its is because the tranny is making pressure now and the mount doesnt control it. Any suggestions.

cool hand

Check both half shafts wear and proper installation. Just when through this on my 92 and the driveside wouldn't clip in because a previous owner used an autozone seal that wouldn't allow it to be installed all the way. I have no idea how long the previous owner dealt with this issue.

chikin pickle

you front mounts not gonna cause vibrations like that. however, chances are that if your front one is shot, one or more of the others is shot too (especially the rear) which would cause those symptoms especially if it is an auto trans with the vacuum hydraulic mount. Along with jerky shifts, engine slamming etc.

dansaleen_04

its not the shafts they are fine and have been fine. the problem started last night. It is a 5spd the side mounts look fine but I havent seen the rear one. The front one is definetly shot.

MAD_MIKE

This. The front engine mount prevents the engine block from rotating towards the firewall. Think of the old, sit in an office chair, throw a tennis ball, and you move backwards physics example. The *crank rotates forward, the block will try to rotate backwards. With the front mount gone, the other three mounts are trying to locate the engine. You are missing a 1/4 or 25% of your engines mounts. The rear engine mount possibly picks up added load, but if the front mount is that far gone the rear mount is possibly just as bad. This leaves the two side mounts which are probably designed more for lateral location than to resist the torsional loads.
Albeit if you removed the hood and drove the car you would see the engine dancing about under load. The drivetrain misalignment that occurs between the axles and transmission are probably causing for the strange loads you are feeling. Oscillations and vibrations are probably being caused by the axles being placed at angles they were not designed to be operated in.

I recommend fixing the obvious problems first, then see if the same issues are still persistent. Probably best to replace all four mounts at this time as they are probably all well worn out.

dansaleen_04

ok let me repeat this again. The shafts were checked and are perfectly fine. They r about 4 months old. IT IS NOT THE SHAFTS AT ALL!!! We pryed the front engine mount a few times last night to the sides but left it at that. This morning we drove the car and it completely stopped shaking which tells me that it is the mount because its the only thing we touched last night.

cool hand

Sounds like you figured it out

dansaleen_04

ok we replaced the fornt mount today and the shaking is still there but a hell of a lot less. We still have not checked out the rear mount which is next on the list. Hopefully it is this since it would make sense. If the front one was replaced and the shaking became lessthe rear would be next because of damage that couldve been caused by the front one breaking. Right???

MAD_MIKE

Never said the root cause of the vibrations was from the axles. I said...
If the front was that badly degraded the rest are probably well worn out.

chikin pickle

Actually, the block moves due to the force of the expanding gasses in the cylinders and the resistance to movement of the piston itself. If you think about it, the crankshaft is rotating within the bearings (lubricated, and smooth the friction coefficient is negligible) so there is minimal force from the crank acting on the block due to friction. The force is minimal from the conrod and piston pin bearings as well. Side loading of pistons accounts for some, but most of it comes from the gas.

Think of the expanding gasses within the cylinders like a spring, pushing down on the pistons and up on the heads. This spring pushes up and down with equal force. If you restrain the crank, the engine will rotate around the crankshaft. The engine is restrained by the mounts, and assuming there is sufficient force produced by these gasses to accelerate the drivetrain the pistons will move, because the engine mounts provide enough resistance that the force of these gasses will be unable to overcome them.

However, you remove the force resisting the block rotation (engine mounts) the engine will spin around the crankshaft as now the inertia of the engine block is much less than the resistance provided by the drivetrain/vehicle and will rotate about the axis of the crankshaft until it is acted upon by an outside force (remains of mount brackets/firewall/etc.)

As for the side mounts, the power from the engine is output offset to the centerline of the system. This creates torque about the center off mass of the engine hence, torque on the side mounts.

Just a little physics to feed the mind.

As for your car, if your front mount is shot, chances are your rear is too. The rears on these cars are almost always ignored, especially by mechanics. Because they are difficult/impossible to visually inspect through the L bracket and obnoxious to replace.

Replace your rear mount. The engine is tilted toward this one, and it sits right above the power steering rack and a main cross beam. It will cause more noticeable vibrations than the front one will.

MAD_MIKE

Yes. It is the crankshaft that rotates and not the engine as an assembly itself. (corrected verbiage in above post)

The point is what is causing the vibrations(bad mounts) not how the torsional load, that is causing the vibrations, is created

chikin pickle

I find that generally things are easier to repair, when a person has a thorough understanding of how that thing works in the first place.

My point was that the engine and the crankshaft are two separate parts, and to explain the purpose of engine mounts and what happens when they fail.

The engine mounts are the reason that the crankshaft rotates, and not the engine. If you don't have engine mounts, the crank remains stationary, and the engine block rotates around the crankshaft.

dansaleen_04

UPDATE:
I found that even after the front motor mount was changed out due to it being torn apart, I still feel the shake but not as rough. What was interesting today was that if you are in 4th or 5th gear and above 4 rpm's there is no shake it goes away. It only happens at lower rpms and at lower gears. Any suggestions?

chikin pickle

Rear mount. Remove it. Replace it.

criscoxxx

I believe that the front and rear mounts on the V6 are computer controlled.

dansaleen_04

I have a 4 cylinder not a V6 but thanks for the info on that didnt know that. I guess I will have to do the unbearable and remove the rear mount just to check it.This is gonna suck!

dansaleen_04

I still do not have a fix for this situation and I am about to let the car go. If this happens I probably will be posting it for parts soon.

TheMuffinMan

iTrader: (1)

You haven't bothered updating if you have tested/replaced the remaining 3 mounts.........

dansaleen_04

thats why I just said still having the same issue. Replaced the rear. sides are perfectly fine almost new in fact.

TheMuffinMan

iTrader: (1)

You didn't note that in any of your posts - go back and reread them, that's why I asked.

If I recall correctly I think it is the EX has the vacuum controlled rear mount - did you connect this correctly or did you replace with a DX/LX mount?

*edit*
Bah, looks like it is the automatic that has the vacuum solenoid mount....disregard

eaglewesman

my brother went through a similar problem, replaced axle a few times. turns out it was some problem in the transmission where the shafts enter. new transmission smoothed it out. not sure if it's relative to your problem but just thought i'd throw it out there. good luck

MAD_MIKE

Have you checked the wheel/tire balance, and verified that there isn't water in the tire? Borrow another set of known good wheels and test drive.