Honda Accord :: 2014 I4 CVT - Tight Steering And Stiff Brake Boost / RPM Fluctuates On Cold Start

My 2014 Accord i4 CVT has 7000miles and it has acted a little strange ever since I pushed it to 3500rpm at Sport mode and then I maybe abruptly shifted it to Drive mode, at which point it made some whining noise shortly. But don’t get me wrong, acceleration was gentle and I don’t ever beat a car.

Since that incidence, it idles at 1500rpm upon cold start at P and fluctuates between 1000rpm and 1100rpm after it warms up a little bit (still in Park). When on stop (brake) on D, it has slight rough idle that periodically comes and goes, which gets better when the A/C is off but not completely resolves. Acceleration is sluggish and lagging, and it has some “dragging/sluggish” feel on coasting as well. When braking, it takes more effort and brake feels stiffer as if it lacks some break boost. Also, the electric power steering gets heavy/tight (I think this could be more of a sensor/input problem rather than the motor).

All these symptoms come and go together except for the fluctuating idle upon cold start, which is persistent. Gently pushing gas at 1200 rpm for, say 10 seconds, tend to “free” the tight steering wheel, and car starts to act more normally with better coasting and acceleration, and more responsive brake for a while. And problem comes back. Also, turning off the A/C seems to make the car act behave notably better but I am cautious of this point since it is known that Honda’s A/C system really takes away the engine power.

I had the dealer shop check for vacuum leak. The report says “check idle, check idle control, check for vacuum leaks ok, check or any codes, checks ok”, basically saying there is no vacuum leak. But I think it is still possible that they missed something. Dealer shops and some independent shops I visited aren’t so willing to figure out what is going on, and I basically need to ask them “check this and check that”.