I'm in need of help ASAP please!! I have an 03 mustang v6 automatic that I recently bought. It had a bad engine so I swapped it out and it ran good for a few months until I started getting a terrible vibration, it tends to shake the worst in between 1300 and 2500 rpms. It does it in park, neutral and while driving. I've replaced both engine mounts, the transmission mount, flywheel, torque converter, full tune up including coil replacement, fuel filter and pump, pcm and harmonic balancer and it's still doing the same thing. I'm at a loss, the car has no misfire and no codes are being thrown. Any ideas would be great, thanks in advance.

 

I noticed you didn't mention the spark plugs. Make sure on those.

Also, and this will sound weird, if it's an engine sourced shake, it could be your alternator going bad. May be throwing some bad signals through the electrical systems.

 

Thanks for the response, I did change the plugs when I did a tune up. Basically changed all the fluids and filters and plugs. The alternator is about a month old and checks out good. The shake is so bad that it makes your whole body itch, I have checked every single nut and bolt on the car and they are all good. I'm baffled, I literally have no other ideas. Car has no misfire, engine runs great but the vibration is unbearable.

 

Do a compression check!

 

Compression and fuel pressure are both good, the shop that attempted the diagnosis checked it. Could it possibly be the internal balance shaft? Do those things go bad?