[Bruce Lancaster]

I think this is well covered here...but I'd add in some more on the pedal itself.
1. return spring should return pedal to top very positively.
2. Bushings...worn out bushings and shaft can produce very eccentric pedal movement and the possibility of pedal stopping at positions other than actual top!
3. Study pedal movement from beneath car, watching as someone uses it smoothly, stomps on it hard, lets it pop up, etc.
4. Around the pedal...a flap of rubber mat or carpet around the hole can do bad things. In other words, once the free play and return are adjusted, be certain that the pedal has actually read the plan and followed along!