The car vibrates/shakes really bad once I hit around 2300RPM until about 3500-4000 RPM or so.. and makes a shaking sound (lol). I'll be taking it into the shop soon, but just wanted to see what it could be. No CEL. I will just swapping plugs and check the compression soon to rule out a bent valve or something.

Behavior:
- car shakes pretty bad
- shifter vibrates rapidly but not move horizontal movement

It happens:
- Only after 2300 RPM or so.. maybe up until 4000 rpm. I didn't really try it above that.
- Regardless if I'm in gear or in neutral
- Regardless if I'm moving or not
- Regardless if I'm 0% throttle or 100% throttle as long as I'm within that 2300-4000 rpm interval.

Does not happen when:
- RPM is below 2000 RPM or so (it gets noticeably better/less vibrations at higher RPMs 4500+)

Notes:
- Checked mounts: I have fairly new Innovative 75A poly motor, tranny and diff mounts. They seem fine visually. I tried moving the engine by hand and it didn't really move.
- Removed aftermarket exhaust and installed stock exhaust. Still there. Not an exhaust leak. I do still have the aftermarket header.. Maybe there's a leak there?
- Checked the bolts for the mounts (seem fine)
- Checked exhaust bolts (seem fine)
- No CEL
- I got a new clutch installed less than a thousand miles prior to this issue happening.
- Stock exhaust is back with a PLM header (issue is still there after removing the aftermarket exhaust and installing the stock one)
- We checked compression and came out to 230, 230, 230, 230
- Leakdown: 15% loss on 2, and 3
- Swapped engine & tranny mounts with OEM mounts and issue is still there
- Swapped plugs, injectors, and coil packs to OEM and issue is still there.

Update (5/2/14):
I took it to Ballade Sports:
- Checked compression and came out to 230, 230, 230, 230
- Leakdown: 2%, 15%, 15%, 2% loss
- Swapped engine & tranny mounts with OEM mounts and issue is still there
- Swapped plugs, injectors, and coil packs to OEM and issue is still there.
- They said they think they notice a misfire
- They are 99% sure it's the motor (bottom end)

Update (10/19/14):
I ended up stopping by a local shop (JMP Auto Werkz) and showed them the issue I was having. The mechanic was convinced that the motor is fine and that he suspected it was something in the clutch/transmission. He dropped the transmission and found an issue with the pressure plate (see pic below). Showed Ballade Sports the pic below and they warrantied the item, installed new clutch and pressure plate, and fixed both of my rear wheel bearings & hubs for their error. Woohoo! I had to tow the car twice and couldn't drive it for a while, but I'm glad it's all sorted now.

 

Does it happen in every gear? It could be as easy as a out of balance tire or possible pitted cv cups. Here's a DIY for the CV cups https://www.s2ki.com/s2000/topic/241...diy-with-pics/

 

It happens even when the car is not moving so it can't be those.

 

Any ideas?

 

Motor mounts?

 

if you have the innovative mounts they vibrate a lot. lol it will setting down over time but it will be noticeable when jumping back into a stock car. I usually have to ask if its running because I cant tell.

 

Did this start happening after you installed the mounts? Could just be you're not used to them, unless you got a bad batch. I'm not sure you can move the motor by hand enough to see if there's play, but you could try Billman's method using a pry bar to see if you can lift the motor up.

 

No, this issue was not there after I installed the motor mounts. It started happening well after I installed them.

 

maybe the nuts backed off? did you check ?

 

I did a visual check, but I will recheck them this weekend when I reinstall the stock exhaust manifold. My aftermarket one might have a leak.