System Too Lean - P0171 (FUEL CONSUMPTION ISSUES)

[Xulfiqar]

Start working on the current codes, and i personally would start with the oxygen sensor code as it throws everything off sync. It can even induce a lean code.

Do you own deeper level scan tools with which you can check the function of the sensor graphically?

[ahmedstudio]

Ok I will start today with oxygen sensors.

No, I do not own any scanner tool. I always have to go to Toyota for their Techstream everytime I need data.

Today I will got for deep scan, what should I look for?

[rajaatta]

oh my god

your oxygen sensor is dead mate fuel system o2 voltage is 0.0V where as O2S2 Voltage is 0.93 which is a clear sign that primary o2 is dead or its Oxygen Sender wire is disconnected or the wire is broken..

your fuel mixture is so rich that the secondary o2 is jumping on its highest on IDLE Condition...

[rajaatta]

these 2SZ are known to fry the primary Oxygen sensors all of which i had analyzed 98% had dying or dead Primary o2 inducing a knocking problem at high rpms and low acceleration due to lean dtc

[Xulfiqar]

I would suggest dont jump into such without self owning tools, And dont use scrap market parts either.

Going to Toyota for every scan will cost you an arm and leg eventually.

[Xulfiqar]

What you mean by overfuelling?

What is breather in valve cover?

overfuelling = more fuel than required (ecu is dumping fuel as it sees that its too lean)

breather in valve cover is the fresh air intake into the tappet cover, its a small hose that connects to air duct.

[ahmedstudio]

I have started cleaning process of primary O2 sensor. I could not detach it's wiring grip so I just disconnected the battery terminals, placed a vinegar filled bottle in engine bay and placed O2 sensor in it. It's been 6 hours and I already saw a lot of rusty particles sitting in the bottle. I also sprayed carb cleaner in holes of O2 sensor. I will keep it dipped in vinigar tonight. Tomorrow I will get OBDII scanned and see if P0130 Oxygen sensor DTC goes away. If not then I wil buy a new sensor. Please advice how to detach the wiring grip of O2 since I also want to make sure it's terminals are in good condition.

[ahmedstudio]

What can I do? A good deep scan device is too costly and o wouldn't need it often. Is there any low price device available?

[Xulfiqar]

who told you to dip it in vinegar? - what will that do anyway? - the connector is generic toyota, it just presses to release its lock.

for starters, get a bluetooth adapter and torque app on your phone, its halfway decent even for this job, the refresh rate is pretty decent too. It wont get you anywhere else than engine though, dont expect to troubleshoot can-bus related stuff.

[ahmedstudio]

@Xulfiqar
I found the leaks responsible for system too lean. Please see the attached image, the particular area of air cleaner assembly which sits right on throttle body is broken

It means too much unfiltered air was sucked in by throttle and that makes me think that a lot of dust must have gone there.

The engine oil has been turning black rapidly due to overfuelling and I also think because of all that dust going in there (am I thinking correct?). Now does the engine need a flush before I change the oil?

I will be installing new air cleaner assembly tomorrow. Should I go for engine flush (if recommended by you guys) and oil change right after that or do I need to check anything else?

[ahmedstudio]

Chris advised to put O2 sensor in vinigar, on Chris Fixes channel on YouTube.

Ok I am going to take it out of vinigar, and will use petrol and later on dry it out with contact cleaner?

Thank you for advising about OBDII scanner.

[ahmedstudio]

breather in valve cover is the fresh air intake into the tappet cover, its a small hose that connects to air duct.

Ok so what should I look in breather in valve cover to rectify overfuelling? I mean to ask what signs, visual inspection should I go for?

[Xulfiqar]

This has a rubber too, that rubber seals it to the throttle housing, where is that?

[Xulfiqar]

dont douse it in petrol either, it will die.

[ahmedstudio]

The rubber is stuck on to throttle

[ahmedstudio]

It's been already 5, 6 hours O2 sensor has been in vinegar. Has it died already?

[Xulfiqar]

connect it back and start it, check the PID for the sensor and see the output on the scan tool.

[Xulfiqar]

was this actively leaking air? - did you check with some spray or something?

[ahmedstudio]

I didn't check with spray. My guess is that throttle has been taking air through that broken area

[ahmedstudio]

I will go for a System Too Lean scan after replacing the aircleaner cover assembly. I am not ignoring another possible reasons for overfuelling