Hesitation while changing Gears and slow C

[Saad]

I own a corolla 2004 e120.. It was originally a manual 2 litre diesel.. But it was swapped to a 1nz-fe (1.5) Automatic by the previous owner... The car performance is really sluggish.. I lost races badly from 1.3 liter engines like Honda city etc.. The car takes too much throttle to reverse or climb hills etc.. It doesn not lauch at all from stop.. When floored it takes about 5 sec to shift into the correct gear and hessitates.. When driven on "D" it changes gear too early like 4000 rpm even when floored.. When driven on manual "1" "2" it drives a bit better gives more power and u can change gears at the rev limiter... Sometimes it feels like it is driving perfeclty.. Giving full performace.. But that happens very rarely.. When driven in Overdrive mode it drives much better.. It changes gears on higher rpm when floored.. But still changes gears earlier.. To solve these problems.. I have changed.. ( Oil Filter. Spark plugs( Not Iridium ) air filter. Fuel Tank filter... It doesnot connect with OBD2 elm327.. Having this problem feon 6-7 months.. Really annoyed from this.. As i am fuelling it for a 1.5 liter car.. But only feels like driving a 1.0 liter c

 

[FinalGear]

The Toyota 1ZZ motor for this generation Corolla/Atis is detuned for fuel efficiency and economical purposes. It's not the Lotus Elise or MR2 turbo charge motor.

Throttle acceleration and hill climbing aren't the highlights of this car.

This car is very picky on spark plugs. I would recommend a set of NGK or Denso Iridium. Change out your old PCV Valve, if you get the chance. See if this gets rid of engine hesitation.

(Expensive procedure)
Change out your transmission filter and fluid. I would recommend only using Toyota transmission fluid only.
Hopefully, this will help with your gear shifting.

Look into a Sprint Booster for throttle assistant (I would recommend it, it's better than an intake air).