car pops out of 4th gear?

Im looking to buy a 1990 toyot celica right now, but the owner told me it occasionally pops out of 4th gear. What exactly is this problem, and is it really something major?

I have never owned a standard car but here's the good news. Your problem might be as simple as the boot being misaligned and it's putting tention on the stick, causing it to pop out. Remove the boot and try driving it (if he wont let you, then don't buy the car). It might also be shifter related, and you might need to adjust the stop points. If the problem is more serious than that, the tranny might be dying (syncro related and what not). The last thing you want to do is replace the tranny on a 1990 (it's worth more than the car all together :S).

Most likely the engagement dogs in the transmissoin are a bit worn. These are the 'teeth' that slide into little 'holes' that actually hold the trans in gear.

The most common situation is that the trans will hold the gear when you are applying power, but only lets go when you release the gas pedal, such as when you slow down.
Usually this gets worse after the trans has warmed up from running. Putting in a more slippery oil like a synthetic will make the problem even worse.

If its only occasional, its a minor annoyance and may not get any worse fro many miles. However, a proper repair of this problem is expensive. The trans would not only require a rebuild but would also require a new gear cluster.
A complete used transmission would be a cheaper option.
I would suggest drive the car yourself, get the trans warmed up and see for yourself how bad it is.

if it's not transmission related and it's just a shifter or a boot problem just buy a short shifter and make your car instantly accelerate to 60 one second faster (a little sarcasm and ricer advice) but it might make your gears easier to find and shorten your shifts if you race. i dont think they cost much.