My car seems like it runs a bit rough at idle (can feel it in the car), and when it hits around 2000 rpm you can actually feel it while driving. It's been this way since I purchased the car several months ago. I had the fuel system cleaned, and it's a little better, but not much.
I have a buddy who has an 88 GT convertible with 5.0 and AOD, and his runs as smooth as a peach regardless. He has 100k on his, and I have 140k on my car. Istill think something is very wrong with my car, and am having a helluva time figuring this out.
The transmission mount and crossmember was replaced right after I got the car. HAs anyone else had this problem, and could it be something like a motor mount?
The engine sounds like it's *missing* when revving (very slightly). I never saw such a difference between 2 5.0 cars in my life, and they're both stock.
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Stock 1992 Vermillion Red Mustang LX 5.0 Hatchback wAOD and new 3:73 gears
I'm going to check the motor mounts...I have my doubts that it's not the problem, though.
My car feels like so hesitant, and so much like a lumbering heavyweight with a rough motor compared to this nimble, smooth and much more responsive 88 'Vert I drove today. Very strange.
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Stock 1992 Vermillion Red Mustang LX 5.0 Hatchback wAOD and new 3:73 gears
I also had the Snap-On engine fuel system flush performed, which made the engine run with much more power. I now have an oil pressure reading on my gauge, versus it being mostly at the bottom end and not moving much. A bottle of Techron fuel system cleaner was added to 12 gallons of 93 octane, after the flush.
At engine idle (900 rpm?) the car shakes a slight bit, like a rough idle. At around 2000 rpm is when it's really audible. With the new rear, at highway speeds it revs around 2k, and the roughness is more noticeable now. At times I can feel it through the floor of the car.
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Stock 1992 Vermillion Red Mustang LX 5.0 Hatchback wAOD and new 3:73 gears
Many different things can cause vibration, I would start with the above quote.
My question is this: is it a vibration or a hesitation ?
also, rare and far between but has someone already removed the vibration damper from the tail shaft of the transmission ?
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1991 LX Convertible 306 C.I.D., GT40 heads and Intake, FRPP E-303 cam, 24lb injectors, MSD 6A, ProComp Coil, 255lph, custom SFC, Custom K member conn., Southside LCA's, Eibach springs, BBK shorties w/ 2.5" H pipe and Flows, C4, Transpro shift kit, 3300 stall, 3:73's w/locker
Many different things can cause vibration, I would start with the above quote.
My question is this: is it a vibration or a hesitation ?
also, rare and far between but has someone already removed the vibration damper from the tail shaft of the transmission ?
It's more like a vibration, like the engine is not running smoothly. It sounds uneven when revved. It's not making the smooth music that it should be. My buddy's 88 convertible is as smooth as my fathers V6 Camry, no lie.
I doubt the vibration damper was removed, but can you tell me what it looks like? I'll try to check it.
I was told the trans was rebuilt at 100k by a dealer, so I guess there is a chance that the damper was removed?
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Stock 1992 Vermillion Red Mustang LX 5.0 Hatchback wAOD and new 3:73 gears
"I took it to someone that says I may have 2 separate issues here. 1) is the rough motor, and 2) the vibration under the floor."
lol. I hope you didn't pay him for that diagnosis.
Anyways, check the harmonic balancer, and it very possibly could be a motor mount. I would also check spark plugs. My truck at a slight roughness/miss to it and it turned out the spark plugs had hairline cracks in them you could barely see.
1992 Mustang LX 5.0 Engine/AOD Vibration? 
