When do you know a Toyota Camry 1997 needs a tune up and what does a tune up entail?

Answer 1

If you have been following the scheduled maintenance guide, you would have done a "tune up" at the prescribed time/mileage interval already. Takes the guesswork out.

US scheduled maintenance guide is at: http://smg.toyotapartsandservice.com/

so if you have missed some services, then it is time for the tune up to catch up.

(if you're really far off, you'll note a loss of fuel economy, perhaps some engine hesitation/less power, maybe even some check engine lights.)

Answer 2

when a spark plugs start missing 0r 70,000 miles plugs and cable air filters