Car violently vibrates when at 2k rpm and above. No audible noise.

2013 Mustang GT Premium

Mods:
Paxton supercharger (stock pulley)
FIC 1000cc injectors
JLT blow-through intake
Remote Tuned
T56 Magnum XL swap
New clutch and flywheel

I'm chasing a vibration issue that has me completely stumped.

The car has a very strong vibration that starts and is the worst at around 2,000 RPM and gets better as RPM increases. The vibration is felt throughout the entire car, but especially in the steering wheel. There are no unusual noises, grinding, squealing, knocking, etc. The engine sounds perfectly normal.

The vibration appears to be completely independent of vehicle speed, gear, or clutch position.
It occurs:
Sitting still in neutral
Moving
Clutch pedal in
Clutch pedal out
Any gear

If I hold the engine at 2,000 RPM while stationary, the vibration is immediately present.
What's making this even more confusing is that the vibration started around the same time the car developed a misfire. I originally assumed the vibration was simply the misfire. I brought the car recently to a shop, and they claim the misfire was tuning-related and that the engine is now running perfectly with no misfires. The vibration, however, remains completely unchanged.

The timing makes it seem like the two issues are related, but fixing the misfire supposedly had zero effect on the vibration.
One thing that may or may not be relevant: I recently installed a T56 Magnum XL transmission, mcleod rxt clutch, and mcleod steel flywheel. However, the car drove smoothly for roughly 300 miles after the swap before both the misfire and vibration appeared, which makes me hesitant to blame the transmission, clutch, or flywheel directly.
At this point I'm trying to figure out what could cause an engine RPM-dependent vibration that can be reproduced while stationary.
Current suspects are the harmonic balancer or engine mounts. But until I get some time under the hood this weekend Im stumped.

Has anyone experienced something similar? Thanks.

The obvious candidate is the harmonic balancer since the vibration is only engine rpm related.
That said if you have headers, make sure they aren't coming into contact with the frame rails. Also check if any engine mounts are shot (the driver's side usually goes first 'cause the torque of the engine pulls it apart).

Supercharged.
+
Misfired.
+
Now vibrates.
=
Need to bore scope the cylinder that misfired. (Or all 8)

Unless the shop has an analyzer/scope to detect & track misfires not sure I'd take that as the final answer. I have a similar setup to yours (sans I have an M122 vs the paxton). That said if you've ever removed and reseated the COPs there's a good chance one or more of them are not seated correctly or the pigtails don't make good contact with the plugs like they used to. The symptoms are exactly as you describe. Horrible vibration around 2k when you try to accelerate. I was about ready to start throwing the parts cannon at it and finally said the heck with it and took it into a Lincoln dealer for a diagnostic. Glad I did, they found two COPs misfiring; moved them to the opposite side of the engine; the misfires followed.
Mystery solved.

Then, they wanted $800 to replace those two COPs. That's a 10 min job (even if you only had one arm). I bought an entire set of OEM COPs. Replaced the two offending units and the car runs great again.

My advice: Pay the diagnostic fee (~$200) and be sure.

Dual Mass flywheel?

Kev555 said:

Dual Mass flywheel?

Click to expand...

No, I am using the Mcleod Lightened steel flywheel

Dino Dino Bambino said:

The obvious candidate is the harmonic balancer since the vibration is only engine rpm related.
That said if you have headers, make sure they aren't coming into contact with the frame rails. Also check if any engine mounts are shot (the driver's side usually goes first 'cause the torque of the engine pulls it apart).

Click to expand...

I checked the engine mounts the best I could, jacked the engine up slowly while the car was running, no change in vibration, also very little movement from engine when revving, they seem pretty solid. How exactly should I go about checking my harmonic balancer? I looked at it from under the car and visually it looked fine, no wobble when the car is running, all the other pulleys look good too. No aftermarket headers (yet).

DieHarder said:

Unless the shop has an analyzer/scope to detect & track misfires not sure I'd take that as the final answer. I have a similar setup to yours (sans I have an M122 vs the paxton). That said if you've ever removed and reseated the COPs there's a good chance one or more of them are not seated correctly or the pigtails don't make good contact with the plugs like they used to. The symptoms are exactly as you describe. Horrible vibration around 2k when you try to accelerate. I was about ready to start throwing the parts cannon at it and finally said the heck with it and took it into a Lincoln dealer for a diagnostic. Glad I did, they found two COPs misfiring; moved them to the opposite side of the engine; the misfires followed.
Mystery solved.

Then, they wanted $800 to replace those two COPs. That's a 10 min job (even if you only had one arm). I bought an entire set of OEM COPs. Replaced the two offending units and the car runs great again.

My advice: Pay the diagnostic fee (~$200) and be sure.

Click to expand...

I did swap my coils around, unfortunately the misfire did not follow, however you saying it was exactly as I describe makes me curious to test it again and check the connectors themselves. I am probably going to bring it to a shop soon if I can figure it out this weekend lol.

milkydoritos said:

No, I am using the Mcleod Lightened steel flywheel

Click to expand...

That's good, with the flywheel hopefully ruled out take Dino's advice on the harmonic balancer as he has a vast knowledge of these models. You may also nee to talk to your tuner again and possibly send them a datalog

milkydoritos said:

I checked the engine mounts the best I could, jacked the engine up slowly while the car was running, no change in vibration, also very little movement from engine when revving, they seem pretty solid. How exactly should I go about checking my harmonic balancer? I looked at it from under the car and visually it looked fine, no wobble when the car is running, all the other pulleys look good too. No aftermarket headers (yet).

Click to expand...

I didn't notice my drivers side engine mount was completely goosed until I removed the engine.

Kev555 said:

That's good, with the flywheel hopefully ruled out take Dino's advice on the harmonic balancer as he has a vast knowledge of these models. You may also nee to talk to your tuner again and possibly send them a datalog

Click to expand...

The harmonic balancer on modern engines is composed of an inner and outer metal ring with the two bonded together by an elastomer rubber sandwich. If that rubber degrades, the outer ring can gradually separate and become misaligned. If the balancer appears to be properly aligned and there's no wobble, it's unlikely to be the source of vibration.

If there are no fault codes for ignition or injector misfires, I'd begin to suspect a possible mechanical misfire. Therefore the next step is to perform a compression test on all cylinders and to bore scope them to rule out the possibility of engine damage.

Dino Dino Bambino said:

The harmonic balancer on modern engines is composed of an inner and outer metal ring with the two bonded together by an elastomer rubber sandwich. If that rubber degrades, the outer ring can gradually separate and become misaligned. If the balancer appears to be properly aligned and there's no wobble, it's unlikely to be the source of vibration.

If there are no fault codes for ignition or injector misfires, I'd begin to suspect a possible mechanical misfire. Therefore the next step is to perform a compression test on all cylinders and to bore scope them to rule out the possibility of engine damage.

Click to expand...

Sounds like the most logical step to me to rule out the cylinders especially with it being boosted. Is it running on Stock conrods?

Religious piston(s) is my bet.