Manuals don’t have a electronic mount. In an automatic, at idle there is additional vibrations where a manual Maxima (which would be in neutral) would otherwise not experience. Therefore, as mentioned, the electric mounts soften at idle and the actuator will then add pressure to the inner rubber once the throttle increases.
The engine mount (electronic one) is controlled by the ECM. The ECM controls the engine mount operation corresponding to the engine speed and the vehicle speed. The control system has a 2-step control (hard/soft). The motor mounts are supposed to harden up when the RPM’s of the motor goes over about 1000 RPM. When it drops below that, they loosen up. At idle with vehicle stopped the mount is soft and when driving the mount is hard.
Most people disconnect them and cut the wire to avoid ECU shortage. It’s been common in some 5thgens and 6thgens. It will not cause a Check Engine Light (CEL) by disconnecting.
Additional Notes:
- The vibration is not even noticeable. I have had mine unplugged for ~6 months and there is no discernable difference at idle or speed.
- There is no reason to disconnect them before they fail. It is pretty easy to tell when they do go bad (buzzing/whirring sound after you turn off the car) and even if you don’t fix it right away nothing bad happens. Mine buzzed for ~2 months before I decided to unplug them.
- As it turns out, the mount is not really an electric mount, it is a hydraulic device. It uses electricity to run a small electric motor that pumps oil in and out of a rubber bladder. Built into the little motor are contacts that are supposed to shut off the motor after it has rotated some certain number of times. As too many members have found out, this design fails and “poof” goes your ECU.
- I ran my 99 i30 with the electric mount unplugged. I read where 5th gens can short out and knock out the ECU. Though I don’t think 4th gens have the problem. Anyway, replacing an ECU on a 99 model can be an expensive ordeal, so I didn’t want to take any chances with the mount’s electric motor causing a short.
- Mine have been unplugged and replaced with ES motor mounts for well over 3 years…..
