Engine knocks when acceleration padel is depressed

[yeh_cheez]

In my Vitz 2011 NEW SHAPE automatic transmission car, it works fine when cold that is the car accelerates normally feeling the power with respect to the depressed accelerator. After a journey of 10 to 15 Km's specially when car goes in the narow streets the car starts knocking when accelerator is depressed to increase the speed lets say from 15Km's/hrs upword.
The knocking sound comes from engine and to reduce the knock I have to stop pushing the accelerator pedal and slowly pressing it again until the car speeds up. I have learnt one thing with expeience that when the engine starts knocking I shift the automatic gear to "S" postion from normal drive "D" position. I can immediatly feel the power and there is no knocking sound but after gaining speed upto 50 to 60 Km's it gives you the sound that the engine is runnung in low gears so I have to change it back to "D" again and it works fine till I reduce the speed around 15 to 20 Km's and then the same knocking will appear again.
Please note their is no engine check light on the display.
I have done the following things to rectify the fault but no results.
I have changed engine oil, sparkplugs,airfilter,oil filter.
Throtal body was cleaned.
In idel condition when engine is running while pressing the acclerator I have checked the exhost and I have seen no smoke.
Please help me out regarding the problem.

[vagabondpiper]

Is it on cng and please mention clearly is it 2011 or 2011 registered ?

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[vagabondpiper]

Have you observed rpm at the time of gear change ?

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[doubletrouble]

do get some high octane on empty tank
get it tuned from toyota
had the same issue....resolved today around 2pm from company workshop ...the guy did tuning to my utmost satisfaction...took couple of hours ...was 30k service...did tuning, brake service, oil change, plugs/airfilter/gasket seals n washels changed...they seemed to be worn out a little...and few more things

[Hesab_Magsi]

had personal experience of 2 vitz and now passo,both cars have same engine as yours so i can say empty fuel tank and then add atleast 20ltr high octane and then mix with petrol then check results.on next refill add 10ltr of high octane always,dont know why these engines have knocking issues.

[saqibnawaz1]

bro i hav the same knocking problm with my vitz 06 new shape but engine check light also turn ON / OFF automatically....

[shaikh229]

do get some high octane on empty tank
get it tuned from toyota
had the same issue....resolved today around 2pm from company workshop ...the guy did tuning to my utmost satisfaction...took couple of hours ...was 30k service...did tuning, brake service, oil change, plugs/airfilter/gasket seals n washels changed...they seemed to be worn out a little...and few more things

How much did they charge u for all this?

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[Naweed]

assuming the fuel is not really sub-standard as in most of Baluchistan and your fuel system is clear ,then in my opinion :

-- first get the valve timing checked as overall it is giving a sign of incorrect timing
-- if that doesn't resolve then your fuel injector are clogged
-- just a far fetched idea .. the thickness of gear oil may also be a reason or something to do with gear .. but this will be last in the check list

knocking is basically missing a stroke or mistimed stroke .. so these two are the main reasons
do not drive for prolonged duration in B or S mode red owner's manual for details

[shahrukh.zaib1]

Hey just read your comment. How did toyota tune your car. I have the same issue checked the cat it is clear, chamged plugs, running hioctane 30:70 mixture. Car is practically new only 14k kms

[shahrukh.zaib1]

How and where was the tuning done. Was knocking resolved