New parts in means updates to the FNR Stealth section

[CoreyB]

Just read your driveshaft write up. I suspect you need new motor mounts to fix the vibration issue under load.

[DG]

I did the motor mounts a couple of years ago. I don't think that's it.

DG

[EvanH]

Reading all of your stuff; You had said the vibe happened after you hit the curb? Do you think the bushings on your front left lower control arm or rear left trailing and control arms got damaged? When power is applied, I would think that could cause a shimmy of the wheel back and forth in a manner that could produce the problem.....Its only a thought, so let me know if I am wrong.

[DG]

The vibe first occurred following the wheel swap. That in turn followed the installation of a pair of 13Gs and the upper Y pipe.

It occurs only under very specific circumstances - high speeds (90-130 km/h) high gear, under load but part throttle (~25% or so or a little higher)

I first noticed it pulling onto a freeway from an on-ramp. I thought I had wandered onto the rumble strips on the side of the road, because that is exactly the sound and frequency of the vibration. It is very violent.

It's not a speed-related issue. It's not that I have a vibration at x km/h, which is normally what indicates a wheel out of balance or something suspension related. Instead, I think it's related to that particular load condition that only occurs in those specific circumstances. That suggests AEM tune related, or possibly a leak somewhere in the intake track that only opens up (enough to matter) under high vacuum.

I know for a fact that I have a stripped bolt hole in the manifold EGR pipe (only recently discovered). It may be leaking enough air into the motor to throw off the tune. Or maybe an injector seal is leaking. I'm not sure. This one is baffling.

The crazy part is the nature of the symptom - the vibration. I know what a misfire sounds like, and this is way too regular to be a "normal" misfire. It could, maybe, be some sort of program-generated misfire (similar to a traction control misfire) - to the point where I double-checked my AEM cal to make sure I hadn't accidentally enabled TC and had some weird parameters turned on that caused it to engage at that time.

Bottom line is that I have a list of known faults and I'm slowly iterating through them. I know that EGR pipe leak needs to be fixed. I know that my injectors are maxxed out so I have a set of DSM injectors to go in (and new seals too). Eventually I'll either fix the fault that rectifies the problem, or I'll exhaust the list of known faults and at least narrow down the list of what it isn't.

DG