I have a 2002 Nissan Altima with the 3.5 v6. It runs good under 1/2 throttle. If you try to accelerate with more that 1/2 throttle, it will bogs down. There are no check engine lights or code stored in the computer.
When driving at 55mph if you try to get the vehicle to downshift to pass someone or pick up speed, the transmission will shift but then it "free revs". It sounds like the transmission is slipping.
I've been told it could be the transmission is bad, the catalytic converters are plugged, and i could have a bad speed sensor.
There 3 converters on the car. I had someone do a back pressure test on the exhaust and they said the secondary cat has 2.5 psi at idle and 5 psi at 2000 rpm (by checking through one of the downstream sensor holes). They were unable to get to the upstream sensors to test the primary cats.
What should we do next? any ideas to what could be causing this problem?