Recently the check engine light came on in my 1998 camry. I suspected the gas tank cap, re-tightended it to hear 3 clicks and the light still stayed on. I jiggled the ignition key thrice and started the car the 4th time and the check engine light went off and stayed off for a week of driving. It came on today. Before taking it in to a dealer I plan to replace the gas tank cap entirely to ensure that its not a leaky gasket on the tank cap. Anyone have ideas ?

Take it to a parts store like TrakAuto or Autozone and ask them to get the codes from your computer so you can get a clue.

it has to be the sensor to the exhaust manifold. Open the hood and it's the one near the middle lower section. Those are randomly replacable as they wear out.

Listen to Brian, why waste money to buy gas tank cap? just like Brian said " Take it to the parts store to get the code, it is free anyway and you will know the result.