Do you have the stamped steel clutch arm on the 4 speed??? Those are junk, and will crack and flex too much to work. You can either weld it up and strengthen it, or get a cas iron replacement. I got mine from a dealer (5 years ago). I think the Fiero Store may have them, too.
Also, the aluminum slave cylinder bracket is prone to breakage. I rebuilt mine with an old Dodge alternator bracket. It's not pretty, but it works. I think Rodney has steel replacements for that.
You will also have to check the clutch arm pivot shaft bushings. They will get thin and cause this problem, but to a lesser degree. You can get the tool and the parts from Rodney.
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"Its a Fiero thing... Heck, even I don't understand!"
Timothy E. Smith
1986 SE V6
1984 Coupe
1996 Ford Probe GT
1999 Chevrolet Silverado Z71
1975 Chevrolet ElCamino SS