Shaking while idle

[broski]

I think I posted this a while back, but i guess ill repost.

Havent been on the forums for a while, but...

I have a 1991 300zx n/a.

When im at idle, my car shakes. not violently, but enough to feel it enough to annoy me. I can actually see the my hood shaking lighting while sitting at a light.

while this happens, SOMETIMES, i will hear a rattle from the bottom of my car, sounds like the exhaust, but i cant be too sure.

this only happens when im at a light. I can be in drive, reverse, park , or neutral and it still occurs.

my RPM is usually below 1k. i have read up that it could be compression issues with one of my pistons, and possibly a piston not firing.

any ideas? i wanna get this fixed asap!

[SvicksTc]

Could be compression or could be something like a dirty MAF sensor or Fouled Plugs Causing the rough idle? Check those out and see how they look

[drew32]

Check the plugs to your coil packs. On my 300 i had one that had a broken clip and would rattle loose. Id drop that cylinder and my car would shake and have a slightly lower idle.

[broski]

how much does it cost to get that done by a mechanic? i dont have the time!!

[blewby u]

Originally Posted by broski

I think I posted this a while back, but i guess ill repost.

Havent been on the forums for a while, but...

I have a 1991 300zx n/a.

When im at idle, my car shakes. not violently, but enough to feel it enough to annoy me. I can actually see the my hood shaking lighting while sitting at a light.

while this happens, SOMETIMES, i will hear a rattle from the bottom of my car, sounds like the exhaust, but i cant be too sure.

this only happens when im at a light. I can be in drive, reverse, park , or neutral and it still occurs.

my RPM is usually below 1k. i have read up that it could be compression issues with one of my pistons, and possibly a piston not firing.

any ideas? i wanna get this fixed asap!

i have the same thing - people told me it could have been the IAC valve or yea, fouled spark plugs. do your revs drop and go up a little bit too? once in a while revs could drop 300 rpm and you'll see your lights dim? i used to run 92 once in a while, now i only run 93 and the problem is a lot better. for me, i'm pretty sure i just need a tune, and i'm waiting on a bolt on before i get a tune, so i can kill 2 birds with one stone. i'd be surprised if it was an issue with pisons, but if i were you, try putting octane booster in it and seeing if it idles better, and is less sporadic.

[OMGz Turbo]

loose motor mount....wait...nvm..

[broski]

hmm
i guess ill try that.
ill do the octane booster and then ill see if i can hit up a mechanic to just look at it. cause its driving me insane bro.

[broski]

Originally Posted by OMGz Turbo

loose motor mount....wait...nvm..

huh? why nvm?

[broski]

Originally Posted by blewby u

i have the same thing - people told me it could have been the IAC valve or yea, fouled spark plugs. do your revs drop and go up a little bit too? once in a while revs could drop 300 rpm and you'll see your lights dim? i used to run 92 once in a while, now i only run 93 and the problem is a lot better. for me, i'm pretty sure i just need a tune, and i'm waiting on a bolt on before i get a tune, so i can kill 2 birds with one stone. i'd be surprised if it was an issue with pisons, but if i were you, try putting octane booster in it and seeing if it idles better, and is less sporadic.

nah my car never low revs to below 500. my lights never dim, or anything....

[blewby u]

Originally Posted by broski

cause its driving me insane bro.

haha i'm a girl, but yea give it a shot. and i dk if i'd have just a 'mechanic' look at it. if you're heavily modded, i'd take it to a specialty tuner place, they'd prob be more familiar with this. when i get mine tuned i'll let you know if mine runs better, too. if u want to check if the spark plugs are oil or carbon fouled just pull them out and check the tips, oil fouled have oil on it, and carbon have black slippery carbon on it, obviously. but you should prob do that too, just so you can check that off your list as not being the reason why, i mean it takes 10 min to check lol so why not

[OMGz Turbo]

I said nvm, becasue after reviewing the problem i was unsure. However my car does the same thing...kinda and i have a bad mount. So i would check there also

[nightblurr]

have you replaced the spark-plugs latley?

[evogsrviii]

if you had a loose mount, you would notice on hard shifting(depending on how bad it is, more than that). do a compression test if you have time, it only takes about 15min. more than likely, the rattle is ur exhaust hitting something. i would check to make sure all the bolts are tight and there isnt a leak somewhere.

[highmilehatch]

These cars are actually notorious for having fuel injectors that go south. It may be running on only 5 cylinders. Try unplugging each coilpack. If the tone of the engine changes, you know that cylinder is gettin fuel and spark. If the tone of the engine does not change, combustion is not happening in that particular cylinder, causing a miss and the shake you are describing. Good luck.