I have a '00 3.8l and it has an engine vibration. at idle 800rpm it just feels like a muscle car with a big cam loping, increase the rpm to 1000 and the whole car shakes like an insane brake pulsation. increase rpm to 1200 and it is back to the loping feel. the vibration comes in and out throughout the rpm range. this is all while the car is in neutral. while driving the car does ok while accelerating or decelerating but maintain rpm and it shakes like a bad rear tire. I have checked motor and transmission mounts all are good, i replaced the coil pack, IAT sensor, IAC valve, PCV valve, i cleaned the EGR valve I have ran 2 bottles of Seafoam through the tank. I scanned the car with a ford scanner and no codes, no misfire nothing, I've even checked the individual header tube temps and they all run very close to the same. I have a manual so it isn't a flywheel weight issue. Any Help would be GREATLY appreciated!

Thanks,
Zack

 

oh and there are No vaccum leaks

 

How many miles are on it?

 

140,000... i also checked the harmonic balancer and it is ok

 

how are your injectors?

ive seen them get stuck wide open and not throw any codes- car ran like ****.