Vibrations after Replacing Front Mount - Replace All Mounts?
 

I recently replaced my front motor mount on my 96 Accord. When I first get the car going it feels a lot smoother, then after awhile when I come to a stop I start to feel vibrations from the engine in the cabin again. It feels better, but they are still there.

I checked the other 2 mounts on the side of the engine and they look ok. The rubber for the mount on the passenger side is intact but it does look a bit old.

The back one... unsure of how to really check it but I noticed steering link solenoid looks like it's broken. Since this controls the idle with a vacuum, could this be the cause?

Should I replace the other mounts too?

slide under the car and grab the oil pan and try to move it front to back if it moves the rear mount is bad

however make sure to jack the engine up slightly at the oil pan with a wooden block in between to avoid damaging then pan so the front mount is level before you tight the through bolt

I was able to spot damaged rear mount from pax side w/ air inlet duct removed.

I had wife put car in R & D w/ ebrake and foot brake set. Small throttle inputs of 1500-2000 rpm will cause excessive engine rotation, particularly in R. I was able to clearly see torn mount rubber.

DIY replacement is a challenge as car must be elevated (ramps I recollect). Several bolts must be released from underneath to enable mount removal. Check DIY forum for posts.

Low idle rpm caused by dirty, blocked IACV will also cause significant vibration. Clean IACV movement, IACV inlet/outlet, throttle plate and bore w/ throttle body cleaner.

good luck

I read on here that aftermarket mounts are stiffer than OEM. Could that be the issue?

Maybe I'm just dreaming I won't need to replace that back mount.

I haven't read of any aftermarket front mounts as causing problems. These are stiff rubber w/ a spoke arrangement to add some flexibility. Aftermarket are same arrangement as OEM.

However, I have read of aftermarket rear mounts causing problems due to stiffness.

good luck

Is there vacuum to the mount when the engine is idling (~700rpm)?

On 4-cyl automatic-trans only, the rear mount is vacuum-operated. Not the front one. It goes into it's "soft" mode when idling in-gear only.

Check out that one...
1. Find the solenoid (#9) on the vacuum line for that mount.
2. Warm up the engine.
3. Get a helper to shift into DRIVE, don't touch the gas pedal, & HOLD THE BRAKE.
4. Unplug the electrical connector for that solenoid. That should make the vibration noticeably worse. If there's no difference, then find out what isn't working.

Solenoid failed? Bad wiring to the solenoid?
No vacuum in that vacuum line? Disconnected vacuum hose?
Maybe the mount itself doesn't hold vacuum?

The RPMs are relatively high at a stop. Usually around 900rpm or just under 1000rpm. I played with idler screw which helped a little bit.

Seems that way to me. I believe part #28 in the diagram is broken from what I can tell when I get under the car and look at the mount. It's a connector to the arm part of the mount.

Set the base idle and let the IACV do its job:

Setting Base Idle speed

If the idle's too high then even a perfect rear mount won't work right.

I noticed it is a lot worse when the A/C is on. I'll try setting the base idle speed.