So my car is a 2002 is300 and it has about 93k miles i bought it a few months ago, manual. When i put it in 1st gear it still goes but it seems to struggle to keep pushing(rpm at 4 and struggling). My worry is that if im on a hill and it is struggling to keep going it could eventually just fail and roll back, or just not push fast enough and hit whoever is behind me. No engine lights are on, my car is in pretty good condition so im wondering if anyone could give me there opinion on what it could be.

 

Sounds like something is definately wrong... It may not have a check engine light on, but it'd be a smart idea to hook a scan tool up and see if there are any misfires, see what the MAF readings are, O2 sensors, etc... Hard to diagnose without more info and without actually seeing the car. From your description, and my past experience.. you likely have a dirty or bad Mass Air Flow sensor.

 

Just cause your check engine light doesnt mean the person before you took it out or the bulb burned out. Have the car scanned and see if any codes appear.

 

I assume your IS is 5 speed manual. Your clutch may be slipping. The easiest way to check is put the car in 2nd gear, parking brake on and slowly release the clutch. If the car not moving or stall, your clutch is gone.