My 2005 HCH (190k miles) seems to have been “changing” over the last 6 month, but I can’t identify the problem. Here is what I believe has changed:
- During acceleration, the engine RPMs are higher than they used to be.
- The level of Assist is higher than it was in the past.
- Gas mileage is 3-5 MPG lower.

I thought that maybe the tranny was slipping, so I took it to a shop that works on the CVTs. They checked codes and drove it, but said it seemed to be normal to them. Up until just recently, there weren’t any codes or CEL. About a week ago, I started getting the code P0420 for the CAT.

I have been focusing on the CVT as the likely culprit, but I have started to develop a theory that I would like to get your opinion on. If, for some reason, the engine was not putting out full power, what symptoms would you expect to see? Would the CVT change the pulley ratio to get a higher RPM (and therefore more torque) for a given accelerator pedal position? Or am I pushing the pedal further to get more torque, resulting in a higher RPM(most likely option)? And would the electric assist motor add more torque since the car is not accelerating as fast as the computer thinks it should?

If the CAT were causing a reduction in engine power, are my symptoms what you would expect to see?

Any advice is appreciated.
Dan

 

P0420 is an upper cat error. If the cat was clogged or otherwise restricting airflow abnormally, then yes, I would expect to see exactly what you are describing.

As for the CVT, I recommend changing fluid every other oil change as you're only changing 3qt out of 5.4qt each time, so about 1/2 the fluid stays dirty. Dirty or low fluid can cause excessive "slip" in the CVT.

I would look to a clogged cat first.

Steve

 

Thanks. I changed the CVT fluid a couple months ago, and no change to the acceleration. And yes, I did use the Honda CVT fluid.

Cars that have a plugged CAT usually have a very smooth flow of exhaust out of the exhaust pipe, rather than the pulsing from each cylinder you would expect with a healthy CAT. This one has the pulses, so not convinced yet that it is the CAT.

I will continue to investigate. And thanks for confirming my theory.

Thanks
Dan