I have problem with idleing.

Last saturay day moring.. I warmed up the car..
and drove like 3min.. Check engine light and
D4 was blanking.. So I turn off the engine and
Turned back on. No lights.. everything was ok.

Same day afternoon ..
I drove the car around the block and it was fine..

This morning (Tuesday)
I had hard time starting up the car.
It took me 4 tries.. with presssing the gas padle to
keep the engine going..

After that while going to detailing shop...
check engine light came on and so I restart up the car again..
No more check light, but idle will not drop
below 1,000.. (1,200 to 1,300)

What could be wrong?

Far as I know.
Check light = O2 sensor
D4 blanking = TCU

Mileage = 170K
- Valve adjustment has been done (last month)
- Replaced Fuel filter (last month)

Thanks for reading.