my car started rattling and then when I would push the gas pedal it would hesitate severely in taking off. I actually had to pump the pedal at times to get it to move. I took it to toyota and they said it was my catalytic converter. The muffler shop said that wasn't it. I had another mechanic check it on the diagnostic machine and it said O2 sensor and catalytic converter. I had these things fixed and still the problem persist. I then had the mass air flow and feul filter changed and it worked well for one day and then it did it again. It sounds like a diesel truck and I can feel it and hear it missing. All this started one month ago and no body knows what my problem is.