Nissan Repair: 2000 Max SE 3.0 6cyl Acceleration Problems, air fuel mixture, acceleration problems

Question
I have a 2000Max SE 3.0 that I've been having problems with acceleration. It drives ok around town but when on the freeway or when trying to pass it hesitates so much that it requires me to press the accelerator more which cause the car to make loud rattling noises(like the engine is knocking). It almost seems like the car goes into a passing gear everytime it hesitate when trying to accelerate. I notice it more so when trying to go uphill. I've already paid $3500 bucks to two different Nissan Dealers for O2 sensors, Catalytic Converter, Fuel System, Starter Motor, Ignition Coils(all 6), Belts, Air Filter but the problem seems worst now that it did in the past. I'm at a lost right now and not sure where to go with this. It's gotten to the point where I'm afraid to drive it on the freeway. Any advise would be greatly appreciated. Thx Norm

Answer
Hi Norm,

Well, it is definitely a sensor problem. Have you had your car scanned and if so, can you tell me the DTCs if there were any? The check engine light should be on when this happens, but can go out when the computer resets. I would love to be able to tell you to just adjust the air/fuel mixture screw, but you don't have one! You do have dozens of sensors though and that's why I asked about the Diagnostic Trouble Codes. Codes can be deceiving. Someone not experienced could interprit the wrong meaning or cause of the code. I feel that with all the repairs you have had, this could be the case. If you don't have the codes, please avoid the dealer and take it to a shop that can scan your car. Cottman Transmissions does this for free. Make sure you get the code numbers and make sure they scan the memory codes also. Resubmit these to me so we can stop the bleeding.