4 months ago, I had a loss of power when accelerating. I replaced the 8 spark plugs and ignition coil and it fixed the problem.
Maybe 1 month ago, the garage replaced the bushings in my front lower control arms. He also removed the splash shield because it was touching the ground, and he said that there was no need for a splash shield (it touched the ground several times over the years and was tied with clips).
Yesterday, there were strong rains and the car drove a few times in deeper water than usual. Since then, the car has a loss of power when accelerating again.
Is it related to the absence of splash shield (which didn't protect against water)?

 

No. The underbody panels in the HCH2 are for aerodynamics and do little to nothing against water infiltration.

 

Today, I drove from Miami to Orlando for a 2 night stay there to enjoy some parks. I didn't drive for so long (4 hours) on the highway since 6 years. Towards the end of my trip, the IMA lamp turned on.My HCH 2008 has 165,000 miles. The battery has been replaced once at 90,000 miles.
I felt more the loss of power when accelerating after the IMA lamp turned on.
What should I do? I have a tight schedule to entertain my daughters in Orlando. Can I drive back to Miami in 2 days and then take care of this problem when I arrive back home?
Does it mean that my IMA battery is going to be dead (and so my car)?

 

O'Reilly Auto Parts - have them check your codes.

 

The next morning, the IMA disappeared so I could return safely from Orlando to Miami.
I disconnected the battery for 1 minute, and there was no error code.
But today, the P0420 reappeared.

 

Did you check the codes when the IMA light came on?

 

No, in Orlando, I didn't have my code reader.

 

Per the above...

Not having your code reader is not an excuse. Autozone and many other parts stores will offer the same free service (unless prohibited by law).

If you have a code reader, there's no good reason to leave it behind when on a road trip... when you would be most concerned about reliability.

Ignoring what your car is trying to tell you is not conducive to reliability.

P0420 is the upper cat. If the CEL comes and goes, your mpg is not significantly reduced, the car is performing well and power is not consistently reduced, it isn't an urgent issue. If it fails and clogs reducing exhaust flow, then it can rob you of power/mpg, and it should be replaced ASAP. Many aftermarket options available. Also worth checking with old-school muffler shops that still do cut-and-weld, who will cut out your old cat and weld in a replacement between the stock flanges. As an example, a new cat for a Prius is about $2K from the dealership (probably about the same for a Honda). I can find local muffler shops locally that will do cut-and-weld for less than $250.

 

OK, I'll remember to bring my code reader for my next long trip. Anyway, I let you know what's the mpg at next gas refill.

 

Here is the latest gas consumption: 33.8 mg. I'm driving in the city with AC always ON (MIami is hot). What do you think?