I just bought a 99 mustang 3.8 anniversary edition. The guy said it needs a clutch cable adjustment. When the engine is running and the clutch is in it is near impossible to get into gear. If I shut the engine off, I can place it into gear easily. Now, I just took it for a spin and I was able to shift around while moving. Not effortlessly but still worked. Im taking it into the shop in the morning but I'm wondering if anyone has encountered this problem or know what it may be? Could the clutch cable really be the culprit?

 

Yes its possible for a cable to stretch, the clutch peddle auto tensioner assembly in the peddle assembly has been known to have issues as well.

 

with the car off put it in first gear, then pull the clutch pedal up with your foot until it clicks, then depress the clutch all the way to the floor. If there is any adjustment left to be had this will do it.

Also, if you are on a level surface with the car running in first gear, does it try to roll with the clutch depressed? If so, it may just need a new clutch assymbly as the pressure plate has gone weak.