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I have a 93 Honda Civic DX that has a problem which has me stumped. It seems that the idle might be a little too high and be causing this, but again, some things make me think otherwise.

When I slow down at a light and come to a stop sometimes the car will begin to vibrate quite hard and sometimes the rate of the vibration lessens, but the vibrations themselves get harder and eventually too great and the car shuts off.

The thing that makes me think that the idle is too high is because when I stop, the car sinks to the ground like it would if you tried powerbraking an automatic FWD, but my foot is completely off the gas. When I let off the brake to go, the car takes off at idle quickly.

Idle speed for the car I would say is around 10mph, but I have a worn speedo sensor that does not register up until ~20mph, so I can't say exactly.

I recently installed a new TPS which tested within spec, and was installed a .5V idle and 4.5V WOT per spec. I also cleaned the FITV valve thoroughly.
The radiator is quite rusty and I am sure that the block has a fair bit of the rust water corroded on it as well but I don't know if this would have anything to do with the way that it is running and how to clear most if not all of the rusty water from the block itself. I have heard of some people taking the water intake and running a garden hose into it and leaving the bottom of the block where it would flow into the radiator to cool open so it provides a constant clean flow of water. Tonight, I rose the front of the car using a ramp and topped the coolant off, turned the heat on high for ~15 minute at idle and let the engine warm up. Topped off the coolant again and then opened the purge valve. I had no air bubbles so I closed it and topped it back off, then lowered it.

Additionally, I do not believe the car has a thermostat. It cools quickly. Say, I idle in park on a summer day and I notice that the temp gauge is high, all I have to do is drive the car at a medium to hard pace and it drops the thermostat level down to near the C, which is where my car usually runs.

I believe I remember reading somewhere that the cars are coolant based, to say that the way the coolant runs through the block greatly affects the way that the motor runs.

 
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I can kill the car when covering the TB.

 
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did you try to see were the vibration is coming from? it might be your rotors if they are bad they warped they will cause vibration and stoping will seem abnormal. as for the idle have you checked the throtle cable. i could be totoally off but try disecting the problem peice by peice you might figure it out that way. good luck.

 
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Sounds like a motor mount to me.

 
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I wouldn't be surprised if its a motor mount. The car has 223k....

But I don't know why sometimes it would be completely quiet and other times vibrate so bad that it shuts off?

It's not rotors. Well, it is, but thats not what I'm trying to fix. The rotors are FUBAR and so are the pads. Those are getting replaced tomorrow.

 
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The title of this thread makes me wanna make a sex toy joke, but I'm refraining...

I wonder how much your engine is saking in the engine bay. If its ridiculously crazy and caused my a motor mount, it could me moving so much that the speed of the crank is affected by the shaking and the engine cuts out... in theory that would seem right, but they travel so fast that that should be impossible, Hrmmm... Check the motor mounts for rips and tears.

If you could, try to take a video somehow so we can see exactly what your talking about.

 
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if its coming from your brakes when you press them, and you can feel it on the brake pedal, it is most like what is called "brake chatter".

 
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if its an automatic i would say your torque converter could be shitting out and partially grabbing while your stopped,if not check those motor mounts