Weird vibration when driving my Z????

[Mikey_ZX]

Hello again everyone,

When driving my 94 Z, I can feel an intermittent vibration coming from the engine. I can especially feel it when I'm stopped or at low speeds. Does anyone know what could be causing this weird vibration? Any suggestions will greatly be appreciated.

[BigTDogg (MA)]

How old are your motor and transmission mounts?

[evildky]

wierd and intermitant leave a lot fo room for interpretation, could be a dead cylinder miss

[Mikey_ZX]

My engine has 129000 miles on it, and it seems like it runs fine when driving. If the motor and transmission mounts are bad, how difficult is the job and is it unsafe to drive the car if those mounts are bad???

[evildky]

does the engine have a good steady idle?

[Mikey_ZX]

When I first start the car the rpm is just above the 1000, once the engine starts to warm up the rpm stays below 1000, around 700 and the gauge doesn't fluctuate. However, sometimes the gauge wiggles a little bit at times when I'm stopped at a light. Also, the car moves forward on it's own a little bit and I can feel the intermittent vibration in the drivers seat, it's a light feeling vibration.

[evildky]

if the engine rpm varies with your "vibration" you have a miss, if the rpm stays steady you have bad mounts, sounds like you have a miss, I'd start by changing the plugs

as for the car moving forward on it's own, you didn't specify auto or manual, it's normal for both actually btu the manual in neutral will have no force behind it

[Mikey_ZX]

Thank you for your help,

I have new sparkplugs, the ngk platinums for my 94 automatic 300zx na. Should I just get the NGK OEM sparkplugs or are these fine??? If I have bad mounts, is it unsafe to drive the Z??? I think I have a bad insulator on the left side of the engine because I compared my Z with the one in the junkyard and mine looks shot, mine looks like it's smashed and corroded. Should this part be replaced?

[robomatic12]

Any plug but the OEM ones won't run properly, start with the plugs.

Take a pic of your mount, does it not look like one piece anymore? Ripped?

[evildky]

a bad engine mount won't hurth anything, the engine still can't move far enough to be an issue

[Mikey_ZX]

Thank you,

I'll replace the plugs as soon as I have time. Do I have to gap the sparkplugs or can I just install them right out the package? However, I checked the engine mounts and from the advice that I have received from you guys, I think the mount looks fine, I must have been looking at that thing when I was drunk. Thanks for your help.

[BigTDogg (MA)]

I'll replace the plugs as soon as I have time. Do I have to gap the sparkplugs or can I just install them right out the package?

they should be close to pre-gapped, but double check the gap with a shim gauge. Should be 0.044" for NAs IIRC.

[jas_mathews]

I think I have a bad insulator on the left side of the engine because I compared my Z with the one in the junkyard and mine looks shot, mine looks like it's smashed and corroded. Should this part be replaced?

If your insulation on the wire is worn, whenever the exposed wire touches metal it will ground out causing that plug not to fire creating a miss.