Random42

So let me start with what I'm currently experiencing and then I'll go back and cover what I've tried to fix the problem.

I currently have two related issues. Firstly, my engine just doesnt sound smooth anymore. This is almost exclusive to accelerating. It mostly sounds like a very light knocking/vibration. 100% based on engine speed not driving speed. Idle sounds pretty normal, some of the time. This leads to issue two. When I first start my car my Idle is pretty smooth, both in and out of gear. However, after the engine warms up, my idle(in gear) gets much much worse. To the point of shaking the whole car. If I shift into neutral or park the vibrations almost go away. Basically I have to shift into neutral at every stoplight for fear of shaking my car apart.

Through all of this not a single code has been thrown so no help from the car unfortunately.

Now a little backstory. This all started about 1000 miles ago with just the engine noise. Very faint at first but again mostly during acceleration. I took it to a mechanic who told me that my trans mount was collapsed and my tensioner pulley was a little squeaky. He also seemed to be pretty confident it wasnt an engine issue as the "engine sounded very healthy". He couldnt hear any roughness to my engine but he did notice a vibration. I ended up replacing my trans mount and both motor mounts with some nice Z1 motorsports urethane replacements. This just enhanced the problem since the mounts are much stiffer than OEM. After that failed I decided to replace my spark plugs. I went for a drive after and the problem almost seemed fixed. However now just a week later its back as bad as before. At this point i have no idea what else it could be.

My car has:
80k miles
RWD
Automatic Trans
no engine mods besides a DIY grounding kit

I've also cleaned the throttle bodies in the past year and checked them again when I did the spark plugs.

Any help would be greatly appreciated as its driving me a bit crazy at this point.

Surfnazi

Run a code logger

ILM-NC G37S

iTrader: (3)

You may want to read this thread as it seems your car is exhibiting the same symptoms: Vibration in Gear

When the car is shaking what is your RPM reading? Anything less than 650rpm's- while in gear- seems to cause this issue. Apparently the only "sure fire" remedy is to have the idle adjusted- unfortunately getting this done is not so simple.

Hope this helps...

Random42

I read through most of that thread, damn what a roller coaster haha. Im pretty sure this isnt my issue. Or at least all of my issue. the vibration i feel is VERY rough. It also seems to be very heat dependent. I'll keep a close eye on my RPMs from now on and update if it is low. I'll also try the code logger advice.

Conboss

Do you still have the Z1 mounts on? Those can make a car vibrate like crazy even on brand new mounts from what I’ve heard. I have thought of replacing with these however I still want my car to be luxurious as it is now.

Random42

Yes i still have the mounts and yes they do increase NVH a little but the issue is sometimes it vibrates and sometimes it doesnt. Also the rough sounding engine was an issue before the mounts. thats what i was trying to fix by replacing them.

PNW_IPL

iTrader: (5)

100 percent the z1 trans mount.
holy crap my car absolutely vibrates to hell.
I'm full bolt on tune with motordymotordyne exhaust z1 trans engine and diff mounts as well as subframe mount. The z1 trans mount was an absolute terrible idea. Guaranteed thats your issue. Not an issue per se but what your looking to fix