Hi All,

My vios ncp93 year 2012

Problem faced :
steady acceleration at 50-60km/h
engine rpm sometimes fluctuate from 1,800 - 1,400 for 1 or 2 seconds then it will go back to 1,800
this issue starts when the bateriku guy chance my battery without engine running.

So far rpm steady at 700rpm when idle, no rpm fluctuate when car is speed up, slowing down or taking corners.


What have i done so far :
1. i have reset the ecu by unplug the battery for 2 hours
2. workshop has clean body throttle
3. change spark plug


i'm still facing the rpm fluctuate problem

Workshop suggest :

1. to buy one unit spark plug ignition coil and test it out one by one to find which plug coil is broken (wallet friendly way)
2. to go back to toyota diagnose the problem


Any good suggestion based on my situation above?
Thank you.

2. to go back to toyota diagnose the problem

Back to Toyota computer diagnostic still can't find the problem. They said everything ok

Only the RPM needle that fluctuates without actually engine jerking?

engine wont jerk coz rpm never go below 1k but it feels heavy like low gear
the symptoms seems less now.

i notice it happens when i release pedal. normally rpm go down a bit or stays.
release pedal will reduce 1k rpm.

I'm confused. The first post says it happens at steady acceleration 50-60kph. Then you said it happens when you release (accelerator?) pedal.

yeah just notice that recently only release pedal rpm fluctuate 400-1000rpm.
maybe when accelerate i just put little push on pedal, sometime its like no push.

Its look like the transmission were "switching" between gear 3 and 4 or 2 and 3. It might be TCU unit or sensor problem?

This post has been edited by Hilmax: Jul 31 2018, 05:01 PM

How much is TCU cost for vios?
i have already change oxygen sensor. what will be other sensors?

Is TCU & ECO same thing?

My guess is the speed sensor malfunction, maybe at that 50-60 km/h the TCU did not somehow receive input from speed sensor.
Sorry i don't know the TCU cost.

my car seems ok liao wor. no more merajuk.
i guess need to stop talking about changing car, i think car hear me

Try to tighten your battery terminal a bit more see whether it helps.

Ok, thanks for the advise. will try it.

Your car is self tuning. Pretty normal

Any updates?

Still sometimes rpm drop a little.

Very seldom happen now. I'm enjoying my ride now