QUOTE(mattp @ Jul 6 2009, 10:57 AM)

where's the cone screw? Is it where the shift rod connects at the firewall or at the transmission?
how can I tell if its the firewall bushing? thanks
Before taking anything apart, take off all the boots and inspect everything for obvious problems... Then
The firewall bushing is in the firewall bulkhead and the shift rod goes through it. If it's gone the rod has to be removed to replace. There is another bushing in the side-shift housing that the rod also goes through.
There are two "cone-screws"
One is behind the firewall (in the engine compartment) at the swivel joint. Pull the boot back from the bulkhead and you'll see it. It's an allen set-screw in the aluminum collar, and it goes into one single hole in the shift rod. This collar has two bushings in it that center a rod. It's part of the joint
The other cone screw is inside the side shifter housing on the transaxle.
You'll have to remove the dust cover and the cone-screw will be attaching the actuator to the shift-rod inside the housing.
If I had one that backed out, I'd use blue locktight (or the equivalent) rather than "waller-out" the hole in the shift rod over time as it loosens. A little heat with a heat gun and it'll let go when you do need to change the bushings... and eventually you will.
If you do this next step, mark (with a marker-pen) the placement of your current collar before you loosen and remove it. Inside the car...
There is another bushing in the shifter itself. It's a plastic donut that centers the shifter as it moves. If it's disintegrated and finally fell out, you will have vagueness and perhaps the symptoms you described. You don't have to get under the car to check that out, but you will have to adjust the shifter from scratch if you take the shifter out to inspect. In case you've not done this before, there are springs under compression so be careful.
There is a fair amount of detail I've left out here. Do a little reading on this forum and the manual before tackling the shifter.
Good luck