GOOD DAY ALL.

I RECENTLY REPLACED THE ENGINE OF MY TOYOTA HIGHLANDER. SINCE THEN I HAVE NOTICED IT DOES RESPOND QUICKLY AND HESITATES WHEN I ACCELERATE.
THIS USUALLY OCCURS WHEN I SLOW DOWN(AT A JUNCTION OR ROUNDABOUT) AND THEN NEED TO QUICKLY ACCELERATE AGAIN-IT THEN HESITATES AND PICKS UP AFTER SOME TIME.
THIS ALSO HAPPEN WHEN I AM MOVING UPHILL.

I HAVE CHANGED THE FUEL PUMP ALL TO NO AVAIL. MY MECHANIC SAYS THE THROTTLE IS SLACK AND NEEDS ADJUSTMENT BUT I AM KIND OF SCARED OF THIS. IS THIS PROPER? ISN'T IT DANGEROUS TO ADJUST THE THROTTLE/ ACCELERATOR?
FELLOW NAIRALANDERS, KINDLY ADVISE ON WHAT TO DO.
THANKS

Anyone got an answer for this?

I think no, idle controlled by ECU, but by changing engine, everything is out of sync (I think)

GUESS THE CABLE WAS DISCONNECTED/TAMPERED WITH WHILE CHANGING THE ENGINE?.
NAIJA MECHANICS ARE SO LOUSY, I USUALLY WRITE OFF ANY CAR THAT HAS HAD ITS ENGINE CHANGED, COS ITS NEVER EVER THE SAME, EVER.

i recommend u disconnect the battery terminals for a while, say 24hrs, or overnight, this shud disable ur ecu/brainbox, cos the brainbox might be having trouble giving precise info to the engine, cos of the engine swap, the brainbox needs to be readjusted to the engine.
then chk the throttle body/idle air control valve of the car

4, use a scan tool to scan the car, though most naija mechanics usally dont hook uo the scan port after performing an engine change.i dont know if its out of carelessness.or to hide the chkengine light from alerting the car owner to hidden unsolved issues!

Possible cause: Vacuum leak, throttle stop or non-signaling of sensor to ECU.

Start with Vacuum lines. Check if any is leaking or left unconnected. If checked out, try all the wiring connectors on the sensors to be sure they are well fixed/tight on the sensors. Unlikely, you can check the throttle stop. If out of adjustment, it can affect the TPS (Throttle position sensor) funtioning properly.i.e telling the ECU the position of the throttle butterfly, as you accelerate,etc. Goodluck.

Ikenna.