1990 300z 5speed BAD vibration from drive train as car slows, engine rpms fall almost stalls as car rolls to stop even though clutch is pressed in, then rpms pick back up...

Hi Sherri,what kind of vehicle you have,need year,make,model.

nobody here will ever do this.
its a hand on job.
get help , live help that can see, touch drive, and hear.
no kidding...

no vibs in neutral, gunning engine fast.
only moving
in a real shop they'd do this on a life, and is very dangerous work
why not let them risk life and limb.

You have a vacuum leak

MAYBE CHECK (MAF) MASS AIR FLOW SENSOR

first check for vacuum leaks, then check idle air control valve.
Please see my tip at http://www.fixya.com/cars/r7427423-fix_poor_idle_high_idle_stalling_fuel . These are generic instructions. If you getstuck or need specific instructions for your car, please get back to me with model, year and engine info.

Torque converter clutch may be jammed.

Check for vacuum leaks, cracked or broken hoses. Clean the throttle body and idle control ports with oxygen sensor safe carb cleaner. Last of all and most important is to get the idle control valve motor tested, it may not be responding quick enough to the sudden change in engine speed to keep it idleing. Also popping the clutch while in your highest gear will not damage anything, at least it never did for me. Don't do it in the lower gears at high speed, it will over rev the engine and that will cause engine damage.

bad engine mount make car shake.cylinder misfire make engine shake.

you need to check the clutch cable is not binding with gas pedal cable. you need to have some body to help you to look the operation at engine area. let me know if this help you

The code says there is a problem, it does not say where in the circuit the problem is, it could be the wiring to the sensors, it could be the PCM (powertrain control module) in your case it sounds like an intake manifold vacuum leak.