my car already hit 11th years old now, clogged 245k km. Summary never had any issues because I did take care of maintenance. However, once heading 170k km onwards, this car's fuel consumption worsens vs. b4 that mileage. especially the city drive. Noted the white smoke on early morning drive b4 car hit optimum temperature.

Things had been done, normal EO change with retaining the manufacturer's viscosity, 0w20, throttle body cleaning, fuel filter change at SC, Iridium spark plug (change per 100k km interval same as manual), few times fuel additive in bottles with varios brands as well as catalytic converter cleaners in bottle form (put it in fuel tank). However, the FC remains as it is. Thus, changing the O2 sensor (my car had 2) will restore the FC? No engine light pops up atm.

bring to workshop and read the o2, airfuel ratio

i changed my O2 sensor, still the same, FC high as F, RM20 only 80 KM . Now need to clean the MAP sensor

Clean all the sensors first.

Usually workshops will replace them during service but if nothing wrong, they leave as it is.

I don't believe in sensors outlasting the car story and will replace every 100k especially the O2 downstream and upstream sensors, MAP or MAF sensors, oil level or pressure sensors and etc.

i done this in the first place cz just needed to unscrew 2 sides. Then I spray it with contact cleaner spray. chatgpt suggest me to change the O2 sensor cz of mileage, max 150k km need to change.

what car? If you have the cheap OBD2 scanner (BT/wifi) that can read your ECU, then may be easier to know whats going on witht he engine and its subsystem. Thing like LTFT. STFT, lambda sensor reading etc can give you an idea on your next step, not shooting in the dark like now.

I think there are some who is well versed in interpreting these ECU readings here that may be able to help you.

multi cylinder engine, single MAF sensor and single lambda sensor
my personal theory, is the injectors are not balanced

let's say cylinder 1, 2, 3, 4...
O2 detect lean, it raises fuel, but one or two injector is feeding less fuel... and so on, you get the idea

possible to change o2 sensor will fix

my vios NCP93 also same, jerking and fuel consumption drop below 300KM 1 tank

after change the front O2 sensor my self , all fix , fuel consumption back to 450km per tank

recommend to change air flow sensor too , if u never change before


by the way my car got show error code on o2 sensor

This post has been edited by minghui415: Apr 30 2025, 01:41 PM

just purchased the O2 sensor for my car online, original, need 2, one at the front and another for the rear. google around, also ask to change after some interval, around 150k km max.
then watch youtube also shown the details, need to change O2 if FC getting worse Youtube

This post has been edited by ayamxxx: Apr 30 2025, 02:46 PM

its a 2014/15 Accord 2.4, T2A. I proceed with the O2 sensor purchase and will install later once receive it.

You can actually clean the O2 sensor with correct solvent, which can dissolve the carbon attached on it

i founded obd wifi function is better than bluetooth /mini? differrnt version numbers

Very hands-on to purchase online and perhaps fix it yourself. Very costly to have the part replaced at Honda's service centre?

there are 2 sets of O2 sensors for my car, the no 1 is easy cz just beside the engine. I already had the sockets to open the O2 sensor, so now waiting for the delivery of it. The No. 2 is behind or below the engine, might as well send it to a nearby workshop for installation.

SC, not just at much2 premium price, but needs to order and takes 2 weeks for delivery. This for my nearby Honda SC

one sensor before catcon, another after catcon. computer want to calculate CO & NOx reduce how much

Changed before proton persona only 1 pc near the extractor. Result very obvious after just changed but will gradually increase back after 20k+ km, when removes, it's covered by black carbon again like the old 1. Root cause could be dirty valves, intake manifold and catalytic convertor which very hard to be cleaned.
Honda car can try clean the egr valve to improves fuel mileage as it's easy to access.

Being able to change any O2 sensor is already considered hands-on to me. I don't even know what an O2 sensor in my car looks like not to mention where is it located. 😅

I ask around for Catalytic converter clean service physically, all quoted rm700-850 for my car. So bought the liquid form and put it on fuel tank, not sure if it effective. Mr Diy also had that nowadays in a bottle form

Ya Liqui moly brand like rm40+ per botol quite expensive. Mr diy aeropak brand cheap only rm10+ but dun know effective or not never try before.

diy black bottle. got effect. lazy to cucuk obd scanner.
smell like diesel mixed.

diy gold bottle. no effect
trimoly shopee live (foc). no effect

mine was p0420 error

Diy black bottle, which one ya. Usually bought Aeropak Throttle body cleaner, saw their Catalytic converter cleaners, quite affordable and 300ml quite generous

In the US, based on YouTube, they all got great feedback after use CataClean bottles. After all, they got annually car inspection, based on certain states, and this CataClean work the effect. Just here, it priced at above rm150 in average and more pricier if Diesel engine

https://my.shp.ee/7zEyhrb getsun

my actual cause was tangan gatal. spray 3bond cleaner into throttle body & intake manifold there.
i guess all dirt went behind stuck

Now that quite some time has passed, mind sharing if o2 sensor change indeed fixed the FC issue ?

yup in my case, able to return the FC as new back. from bad reading of 8.8km/l (combined city + highway) to now 13.3km/l with similar drive.

For oxygen sensor, how many km do we need to change it? Cuz my old camry acv30 year 2003 already clocked 411 000km plus, the fuel consumption very good

scan with obd reader first

Okey, will scan it first, thank you

o2 value changing according to u pijak pedal.
means ok. want value range (in depth), need google him out

Two stages, if O2 sensor already not functioning, engine light will pop up intermittently or heading bad, permanently. This happened to my office pickup car, Triton with 300+k km, and SC Mitsubishi just put reset via reader, but the issues will return back. Until office guy send outside workshop and put new sensor, no more engine light pop.

On my car, since use it since new, kinda knows on what the FC average I get per refuel, and when passing 200k km, the FC kinda went worst. Done the normal EO change, atf oil, fuel filter, spark plugs but FC remain the same and not as new. Until change this O2 (my car had 2 of it), the FC restore back. Surprisingly able to hit 17km/l from JB - Kajang on meter, but at 110-120kmh consistent drive, quite tiring

This post has been edited by ayamxxx: Oct 21 2025, 06:45 PM

Okey, at least if engine light pop up i dont panic as it is indicator of the oxygen sensor, if so i will scan it first to detect the main issue, surprisingly my acv30 2.0e camry fc still good so nothing to worry about at the moment, but always be ready 😏🔥

P0421 is o2 sensor related?

chatgpt said yes related to O2 sensor

Washed sensor, reset error. Wait and see