Toyota vitz 2014 facing low mileage issue in city about 7 to 8 Km/L in city

[nusairsoomro]

Dear PakWheels Colleagues,

I have Vitz model 2014 1KR 1.0. done 90 thousand Plus KMs. I am facing issue of fuel economy as it is consuming about 7-8 KM/Ltr. The consumption was fine when i bought the car but recently it dropped. Also i have replaced ignition coils, sparkplugs, serviced cat and its sensors and also fuel injectors cleaned. But consumption is same no improvement. Apparently, there is no missing, no vibration no sound and everything is normal. I asked my mechanic to scan it again and found error of O2 sensors but whereas no engine light was on. We tried two three times but same engine light was not appearing. We also dismantled he meter and check for any forgeries but not observed.
Can any one advise what will be the cause of this issue? Is issue with car meter? Or any other wiring or fuse issue? Or actual o2 sensors are faulty?

My mechanic suggested me to first inspect and repaired the meter then we will check the O2 sensor and its wiring. Will replace them if it required.

Thanks.

[askai37]

o2 sensor became lazy after 80000km. best is to change with new one. some scanners show o2 graph. a good 02 oscillate sinusoidal waveform at idle. you cannot get check engine as long as o2 is giving signal. best to check graph of 02

[pwuser161074925342]

Bro engine overhaul k bd kia ehtyaat krni cahhye

[nusairsoomro]

Thank you so much for you prompt and helpful feedback i will asked the mechanic to scan the engine as you advise me. Furthermore can you please advise regarding the engine check light issue why it is not on if O2 is not working?

[omaruser156370259465]

Which engine oil brand + grade are you using?

[nusairsoomro]

I am using shell 5w30 blue can. Recenlty changed it only 500 to 600 km are completed so far.

[askai37]

check engine comes either any of the sensor or electronic equipment is open or short circuit. as long as sensor have resistance engine light will not come on. for your experiment just pullout connector of o2 sensor and start the car you will see check eng light. stop car and reconnect the light will disappear. if not remove battery and reconnect.

[nusairsoomro]

Ok thanks a lot for guidance. Tomorrow i will follow these steps and update you accordingly.

[nusairsoomro]

Checked that way as you advised but no check light observed on meter. Even engine check light is not showing when we only on the engine switch. Can you please what whould ve the cause of this issue?

[askai37]

engine light bulb in meter is gone if not coming on ignition on.or ecu connection to meter is open. so many probabilities. seek electrician help. or use high end scanners or toyota tech stream to check and activate cluster lights

[nusairsoomro]

Thank you so much for your help and guidance. Just checked the merer it was bypassed with jumper wire. We have rectified it. Furthermore both oxygen sensors were not changing there volts on engine ideal running and also graph were showing straight line. We replaced both sensors and also verified the complete loop. We test drive the car its drive was smooth as compare to peevious and initially during drive test its milage was improved to 11 to 12 but slowly slowly it again dropped to 7 to 8 dnt know why. But my speed was around 40 to 50 due to traffic so may be this is the cause but i dnt understand why its milage dropped on meter all of sudden, can you guide me further on this.

[askai37]

when u reset avg meter it shows high values in start then settled down. regarding avg of car check fuel filter to injector and use correct spark plug for your engine and set specified gap. usually toyota engines has 1.1mm spark gap

[nusairsoomro]

Ye exactly, fuel filter and injector is cleaned month ago and spark plugs replaced with SC16HR11 original japan make. I think spark plug gap was not checked installed as new condition.

[askai37]

SC16HR11 is replaced by SC20HR11. r spark plug original as in market sc16hr11 is not available check originality of yur plugs.
2ndly fuel filter cleaning is not suggested. replace fuel filter if not available in market check daraz.

[capsat]

if there are no error codes upon scanner. It is time you shall calculate the fuel consumption using tank top up method.

Fuel avg over cluster is always misleading. specially in city wide traffic drive.
Top up tank reset odo trip meter, note down main odometer reading. & quantity poured.
drive car as usual after half tank or 200 kms, go back to same station same dispenser top up again. note down odometer and trip meter A - reset again drive .

at half tank or 200 km run top up note down qty poured, repeat - 2 more times

that will give you per litre km consumption which may be quiet different then fuel avg display over cluster.